The research findings showed that coal contains a significant amount of mineral matter that is mainly composed of clay and quartz, which can be easily seen through petrographic analysis. The study also identified that the predominant minerals in Sekoko coal are clay, pyrite, quartz, and carbonate minerals. Organic petrology revealed that inertinite is the most dominant maceral group, followed by vitrinite and liptinite. The vitrinite reflectance value ranged from 0.6 to 0.7. Coal from Sekoko coal mine is enriched in Fe2O3 while host rocks depleted in Fe2O3. X-ray fluorescence microscopy shows Fe2O3 mean concentration of 1.18 Wt% in coal and Fe2O3 mean concentration of 0.45 Wt% in host rocks. In conclusion, coal was of medium rank bituminous C. Significant amounts of pyrite are present in coal, mostly towards the south of seam 10 as opposed to the west. The host rocks of the Sekoko coal mine showed no signs of pyrite mineralization. The study recommended screening and washing of coal prior utilization to help improve coal quality by reducing the amount of sulfur content in coal. Keywords: Waterberg Coalfield, Sekoko Coal Mine, Petrography, Mineralogy, Geochemistry.

1. i
Faculty of Science, Engineering and Agriculture
Department of Earth Sciences
Petrographic and Mineralogical Investigations of Coal and Host Rocks in Sekoko
Coal Mine of the Waterberg Coalfield, Limpopo Province, South Africa
BY
Netshisaulu Humbelani Justice
Student No: 18001288
A mini dissertation submitted to the Department of Earth Sciences, Faculty of
Science, Engineering and Agriculture at the University of Venda in partial fulfilment
of the requirements of the degree of Bachelor of Earth Sciences in Mining and
Environmental Geology
Supervisor: Dr H.R. Mundalamo
Department of Earth Sciences, University on Venda
February 2022

2. ii
DECLARATION
I, Netshisaulu Humbelani Justice, declare that this mini-dissertation is my own
unaided work, except where otherwise acknowledged. It is being submitted for the
degree of Bachelor of Earth Science in Mining and Environmental Geology at the
University of Venda, and it has not been submitted for any degree in any University.
Signature Date
22 – 09 – 2022
Supervisor’s signature Date
……………………………….. ………………………………..

3. iii
DEDICATION
This mini-dissertation is dedicated to my late Father Mr A.N. Netshisaulu for being a
father, a friend and a role model. May your soul rest in peace.

4. iv
ACKNOWLEDGEMENTS
Firstly, I would like to thank the Lord almighty for divine wisdom, diligence and
strength to complete this project. I can do all things through Christ who gives me
strength.
My sincere gratitude goes to my dear parents, the late Mr A.N. Netshisaulu and Mrs.
M.O. Matidza for emotional, moral and financial support.
My heartfelt appreciation and thanks to my supervisor, Dr. H.R. Mundalamo for
guidance, motivations and scientific inputs throughout the research work. This work
would not have been possible without her positive critics and splendid supervision.
My deepest gratitude extended to Mr. K.T. Ramphabana for sharing his knowledge
pertaining both to the research work and other aspects related to the discipline of
Earth Sciences in Mining and Environmental Geology, thank you for you excellent
mentorship. To Mr T Mphanama, thank you for your valuable inputs and comments.
I am grateful for the motivations and encouragement, moral and emotional support
from Dr. F. Amponsah-Dacosta. I wouldn’t have made it without your guidance.
I also would like to thank my associates in the Waterberg project, Miss. P.J.
Mothatha and Miss. R.I. Mankoe for the helping hand during the laboratory work as
well as the support and encouragement.
To my Pastors R.M and L.M Khauli, thank you for keeping me in your prayers and
Miss. Z. Maguvha, thank you for the unwavering encouragement and support.
I am grateful for the support from my siblings, friends and classmates.
The Lord bless you all!

5. v
ABSTRACT
The majority of South African coalfields, including the Waterberg coalfield, have
undergone extensive exploration and exploitation, but little attention to Sekoko coal
mine, leading to lack of information on geology, mineralogy, and geochemistry. This
study therefore aimed at the petrographic and mineralogical studies of host rocks
and coal mine.
Sampling was undertaken within the box cut at Sekoko coal mine. A total of 18
samples were collected (3 host rocks and 15 coal samples). 14 coal samples were
collected from the box-cut and 1 composite sample from stockpile. Petrographic
microscopy was undertaken to investigate the organic and inorganic constituents of
host rocks and coal. X-ray diffraction spectroscopy was undertaken to investigate the
present mineral phases in host rocks and coal. To supplement the mineralogy data,
x-ray fluorescence spectrometry was done to determine the geochemistry of both
host rocks and coal.
The research findings showed that coal contains a significant amount of mineral
matter that is mainly composed of clay and quartz, which can be easily seen through
petrographic analysis. The study also identified that the predominant minerals in
Sekoko coal are clay, pyrite, quartz, and carbonate minerals. Organic petrology
revealed that inertinite is the most dominant maceral group, followed by vitrinite and
liptinite. The vitrinite reflectance value ranged from 0.6 to 0.7. Coal from Sekoko coal
mine is enriched in Fe2O3 while host rocks depleted in Fe2O3. X-ray fluorescence
microscopy shows Fe2O3 mean concentration of 1.18 Wt% in coal and Fe2O3 mean
concentration of 0.45 Wt% in host rocks.
In conclusion, coal was of medium rank bituminous C. Significant amounts of pyrite
are present in coal, mostly towards the south of seam 10 as opposed to the west.
The host rocks of the Sekoko coal mine showed no signs of pyrite mineralization.
The study recommended screening and washing of coal prior utilization to help
improve coal quality by reducing the amount of sulfur content in coal.
Keywords: Waterberg Coalfield, Sekoko Coal Mine, Petrography,
Mineralogy, Geochemistry.

6. vi
TABLE OF CONTENTS
DECLARATION ......................................................................................................... ii
DEDICATION............................................................................................................ iii
ACKNOWLEDGEMENTS......................................................................................... iv
ABSTRACT ............................................................................................................... v
LIST OF FIGURES.................................................................................................. viii
LIST OF TABLES ...................................................................................................... x
LIST OF ACRONYMS AND ABBREVIATIONS ....................................................... xi
CHAPTER ONE: INTRODUCTION............................................................................ 1
1.1 Background.......................................................................................................... 1
1.2 Study Area ........................................................................................................... 3
1.2.1 Location of the Study Area ................................................................................ 3
1.2.2 Climate.............................................................................................................. 4
1.2.3 Topography and Drainage................................................................................. 5
1.2.4 Soil and Vegetation ........................................................................................... 5
1.3 Problem Statement .............................................................................................. 6
1.4 Justification .......................................................................................................... 6
1.5 Research Questions............................................................................................. 7
1.6 Objectives ............................................................................................................ 7
1.6.1 Main Objective .................................................................................................. 7
1.6.2 Specific Objectives............................................................................................ 7
CHAPTER TWO: LITERATURE REVIEW................................................................. 9
2.1 Regional Geology of South African Coalfields...................................................... 9
2.2 Local Geology .................................................................................................... 14
2.3 General Overview of Prominent South African Coalfields .................................. 16
2.3.1 Witbank Coalfield ............................................................................................ 17
2.3.2 Highveld Coalfield ........................................................................................... 18
2.3.3 Soutpansberg Coalfield................................................................................... 18
2.3.4 Waterberg Coalfield......................................................................................... 19
2.4 Mining History .................................................................................................... 19
2.5 Coal Petrology.................................................................................................... 20
2.6 Coal Mineralogy ................................................................................................. 23

7. vii
2.7 Environmental Impacts of Coal .......................................................................... 25
2.8 Stratigraphy of the Waterberg Coalfield ............................................................. 26
2.9 Laboratory techniques........................................................................................ 30
CHAPTER THREE: MATERIALS AND METHODS ................................................ 33
3.1 Preliminary Study ............................................................................................... 34
3.1.1 Desktop........................................................................................................... 34
3.1.2 Reconnaissance Survey.................................................................................. 34
3.2 Field Work.......................................................................................................... 34
3.2.1 Sample Collection ........................................................................................... 35
3.3 Laboratory work.................................................................................................. 37
3.3.1 Sample Preparation......................................................................................... 37
3.3.1.1 Sample preparation for Petrographic Study of Host Rocks .......................... 37
3.3.1.2 Sample preparation for Mineralogical analysis using XRD........................... 38
3.3.1.3 Preparation for Whole Rock Geochemistry .................................................. 40
3.3.2 Sample Analysis.............................................................................................. 40
3.3.2.1 Petrographic Study....................................................................................... 40
3.3.2.2 Mineralogical Analysis of Host Rocks and Coal ........................................... 42
3.3.2.3 Whole Rock Geochemistry Analysis............................................................. 43
CHAPTER FOUR: RESULTS AND DISCUSSION.................................................. 46
4.1 Characterisation of Host Rocks and Coal........................................................... 46
4.1.1 Description of Host Rocks............................................................................... 46
4.1.2 Description of Coal Samples........................................................................... 49
4.1.2.1 Maceral Point Count..................................................................................... 50
4.1.2.2 Vitrinite Reflectance ..................................................................................... 58
4.3 Mineralogical Characterisation of Host rocks and Coal...................................... 59
4.4 Whole rock geochemistry ................................................................................... 64
CHAPTER FIVE: CONCUSIONS AND RECOMMENDATIONS ............................. 66
5.1 Conclusions........................................................................................................ 66
5.2 Recommendations ............................................................................................. 67
Reference................................................................................................................. 68

8. vii
i
LIST OF FIGURES
Figure 1.1: Locality map of the study area 3
Figure 1.2: Mean annual rainfall 4
Figure 2.1: Geological map of the study area 16
Figure 2.2: Coalfields of South Africa 17
Figure 2.3: Stratigraphic column of the geology of the coal-bearing sequence
of the Waterberg Coalfield
28
Figure 2.4: The Grootegeluk Coal Mine, coal zone/Mining benches 29
Figure 2.5: Schematic representation of an X-Ray Fluorescence 32
Figure 3.1: Flow chart summarising the methods and procedures applied in
this study.
33
Figure 3.2: Sampling from the box-cut. 36
Figure 3.3: Sample collection from the stockpile. 36
Figure 3.4: Procedure for preparation of thin-sections 38
Figure 3.5: Procedure for preparations of samples for X-ray fluorescence
spectroscopy.
39
Figure 3.6: Olympus BX51 transmitted and reflected light petrographic
microscope used for petrographic study of rock specimens.
41
Figure 3.7: Zeiss Axioimager organic petrography microscope used for
maceral point count and vitrinite reflectance studies
42
Figure 4.1: A diagram showing a gritstone specimen (Ply A F-R) (A) collected
from the roof of seam 10 on the west portion of the box cut and
Photomicrographs (B and C) of the specimen under a
petrographic microscope. Mc= Microcline, Qz= Quartz, Cl= Clay,
C= organic matter
47
Figure 4.2: A diagram showing a gritstone specimen (Ply A F-R) (A) collected
from the roof of seam 10 on the west portion of the box cut and
Photomicrographs (B and C) of the specimen under a
petrographic microscope. Mc= Microcline, Qz= Quartz, Cl= Clay,
48
Figure 4.3: A diagram showing a gritstone specimen (Ply A S-L) (A) collected
from the roof of seam 10 on the south portion of the box cut and
49

9. ix
Photomicrographs (B and C) of the specimen under a
petrographic microscope. Mc= Microcline, Qz= Quartz and Cl=
Clay
Figure 4.4 Hand specimen showing alternating bands of bright and dull coal:
(A) alternating bands of dull and bright coal, (B) thin bands of
bright and dull coal
50
Figure 4.5: Major maceral groups in coal. 51
Figure 4.6: Micrographs showing identified Vitrinite (VIT), Inertinite (INT)
macerals, taken under white reflected light using an oil immersion
lens for Seam 10 Ply C F-R.
53
Figure 4.7: Micrographs showing identified Vitrinite (VIT), Liptinite (LIP)
macerals, taken under white reflected light using an oil immersion
lens for Seam 11 Composite sample.
54
Figure 4.8: Micrographs showing identified Vitrinite (VIT), Inertinite (INT) and
Liptinite (LIP) macerals, taken under white reflected light using an
oil immersion lens for Seam 10 Ply C S-L.
55
Figure 4.9: Micrographs showing identified Vitrinite (VIT), Inertinite (INT),
Liptinite (LIP) macerals, grain of Pyrite (P) and fractures, taken
under white reflected light using an oil immersion lens for Seam
10 Ply H S-L.
56
Figure 4.10: Micrographs showing identified Vitrinite (VIT) macerals, taken
under white reflected light using an oil immersion lens for Seam
10 Composite.
57
Figure 4.11: Micrographs showing identified Vitrinite (VIT), Inertinite (INT)
macerals, Kaolinite clay and Quartz grains (Qz), taken under
white reflected light using an oil immersion lens for Seam 10 Ply F
S-L
57
Figure 4.12: Mineral distribution in coal and host rocks 61
Figure 4.13: Mineral matter content associated with coal. 62

10. x
LIST OF TABLES
Table 1.1: Average temperatures per months in the Waterberg
region, Lephalale, South Africa
4
Table 2.1: Macerals and maceral group description of coal 21
Table 3.1: Quantitative mineralogy of coal and interburden 43
Table 3.2: Concentrations of major oxides in clastic sedimentary rocks 44
Table 3.3: Concentrations of major oxides in coal 45
Table 4.1: Maceral group data analysis 52
Table 4.2: Vitrinite reflectance data analysis 58
Table 4.3: Coal rank classification using vitrinite reflectance (%RoVmr) 59
Table 4.4: Mineral matter data analysis 62

11. xi
LIST OF ACRONYMS AND ABBREVIATIONS
AMD Acid Mine Drainage
GCM Grootegeluk Coal Mine
GIS Genetic Increments of Strata
GSSA Geological Society of South Africa
GUS Genetic Units of Sedimentation
ISCOR Iron and Steel Corporation
MKB Main Karoo Basin
SABS South African Bureau of Standards
SACS South African Committee of Stratigraphy
SME Society for Mining, Metallurgy and Exploration
XRD X-ray Diffraction
XRF X-ray fluorescence

12. 1
CHAPTER ONE: INTRODUCTION
1.1 Background
Smoot (1979) defined coal as a black, non-uniform organic fuel created mainly from
plant material that has undergone partial decomposition and metamorphism. The
process of formation happens over a long period of time such that the material is
under pressure of the overburden long enough to decay. While coal is classified as
non-renewable resource by some, most resource economics consider coal as a
renewable resource due to its vast remaining stock although its use leads to its
depletion (Khanna, 2001). Khanna (2001) also stated that the estimated
consumption rate is about one billion tons per yearand therefore there is enough
coal to last 3000 years.
Coalification (Coal diagenesis and metamorphism) is a function of heat and pressure
acting over time (O'Keefe et al., 2013). Therefore, the rate of metamorphism, the
amount of carbon present in coal, and the amount of heat the coal produces, is
responsible for the characterisation of coal into 4 main stages. This includes the first
stage being Peat, followed by Lignite, Bituminous and Anthracite. The quantity of
pressure and heat that plants underwent over time determines the kind of coal
deposit, as explained by Stracher et al. (2010).
South Africa relies heavily on coal-generated energy, making it the world's sixth-
largest producer of coal. Most of its coalfields have been explored and exploited. An
estimation of the coal reserves left is about 30 billion tons (Moumakwa, 2009) and
with the current production rate and high demand for coal, the remaining coal may
last only 4 – 5 decades. Prominent coalfields therefore include Witbank, Highveld,
Ermelo and Waterberg with an estimate of 75 billion tons of coal, 50% of which has
been exploited and 50% of the remaining resource being mined (Moumakwa, 2009).
During a water drilling project in 1920 on Grootegeluk farm in the north-western
Transvaal, the Waterberg coal was first discovered, as noted by Faure (1993).
During the 1940s, the Geological Survey of South Africa (GSSA) conducted
additional exploration which defined the size of the coalfield known today as the

13. 2
"Waterberg coalfield." As noted by Faure (1993), the Iron and Steel Corporation
conducted comprehensive exploration after that and founded the Grootegeluk coal
mine.
According to Moumakwa (2009), the Waterberg coalfield in the Grootegeluk
Formation is largely unexplored and could be viewed as the future of South African
coal. Many people believe it could replace the Central Basin (Witbank, Highveld, and
Ermelo coalfields) as the primary coalfield, as noted by Jeffrey (2005). This is due to
the Waterberg Coalfield containing a greater quantity of South African bituminous
coal reserves in situ (Dreyer, 1991). The Waterberg coalfield has been recognized
as the continental powerhouse for electricity generation fueled by coal (Waterberg
Municipality, 2013).
The Waterberg coalfield is highly faulted and all the structures and their effects have
not been studied to date (Fourie et al., 2009). The more recent Daarby Fault cuts
across the Waterberg coalfield dividing the coalfield into a shallow deposit minable
on the surface and the other deep minable underground. According to Bester and
Vermeulen (2010), coal bearing rocks in this coalfield are bounded by the Limpopo
Mobile Belt to the north and the Eenzaamheid and Ellisras faults to the north.
There are two coal mines operating on this coalfield namely, Grootegeluk coal mine
owned by Exxaro mine and Sekoko Coal mine which has no documented information
about the coal in the mine. The upper zone of coal in the Waterberg Coalfield forms
in the Upper Ecca group (Volksrust formation) and is characterised by the bright
coloured coal while the lower zone forms in the Middle Ecca group (Vryheid
Formation) and is characterised by dull coal (Prévost, 2011).
This study therefore, focused on the petrographic and mineralogical characterization
of host rocks and coal in Sekoko Coal Mine, Waterberg Coalfield. This was done in
order to gain understanding on the occurrence of sulphide and carbonate minerals in
coal and the host rocks and their potential to generate acid mine water.

14. 3
1.2 Study Area
1.2.1 Location of the Study Area
The Sekoko coal mine is located in the Waterberg basin in South Africa, Limpopo
Province, about 10 km west of Lephalale. It is found within the Waterberg Coalfield
which extends from the town of Lephalale in the east to west of the town
Steenbokpan in the west, and up to the border, with Botswana in the north
(Vermeulen and Bester, 2009) (Fig. 1.1). This coalfield extends about 88 km east to
west and about 40 km north to south (Aphane and Vermeulen, 2015) covering an
area of more than 2300 km2 (Vermeulen and Bester, 2009).
Falcon (1988) and Fourie et al. (2009) both stated that the Waterberg Coalfield is
situated in between two northern and southern faults that act as boundaries to this
coalfield, Melinda fault and Eenzaamheid fault respectively. The Botswana border
acts as the western boundary of this coalfield (Hancox, 1998).
Figure 1.1: Locality map of the study area (ArcGIS 10.8, 2022).

15. 4
1.2.2 Climate
The study area is characterised by dry and wet seasons. The period between
November and March is typically the wet season, while the dry season lasts from
May to September, with relatively cooler temperatures in June and July and hot and
humid conditions in August. April marks the onset of autumn and is a transition
month, while late September to early November is considered the spring season.
The study area has a mean annual rainfall of about 600 mm (Waterberg municipality,
2013). According to Bredenkamp et al. (1996) average daily maximum temperatures
vary between -5°C in and 40°C with an average of 21°C. During summer’s days,
daily maxima of ˃40°C are common (Fig. 1.2) and Table 1.1.
Figure 1.2: Mean annual rainfall (Roux, 2015).
Table 1.1: Table showing average temperatures per months in the Waterberg region,
Lephalale, South Africa

16. 5
1.2.3 Topography and Drainage
The Waterberg region is characterized by mountainous areas and is named after the
Waterberg mountains (Waterberg, 2013). The main topographic feature in the study
area is the Waterberg Mountain range, which is a large plateau with steep
escarpments to the south and east, including the Waterberg plateau, Transvaal
plateau, Pietersburg plateau, and Limpopo depression. The mountain range is
mostly composed of sandstone hills and mountains (De Klerk, 2004).
The Waterberg District Environmental Management Framework identified five
catchments within the study area, which include the Lower Crocodile River Sub-
catchment, Mokolo River catchment, Lephalala River catchment (a sub-watershed of
the Limpopo River), Mogalakwena River catchment (a major tributary of the Limpopo
River), and a small section of the Olifants River catchment. All of these catchments
drain into the Limpopo River, which runs along the north-western boundary of the
study area. The Mokolo River is responsible for collecting most of the drainage from
the Waterberg Massif and discharging it to the Limpopo River.
1.2.4 Soil and Vegetation
According to Waterberg Municipal (2013), the soil type in the study area is diverse. It
has weakly developed soils formed from sandstone and quartzite on mountainous
catchments, uplands and rocky areas, red and yellow. Freely draining sandy soils
which are acidic soils of low fertility found in high rainfall areas and plinthic upland
duplex and Para duplex soils on undulating mid-level are also found within the study
area. Rugged terrain derived from sandstone quartzite and shale and are utilised as
arable land with high risk of erosion.
The Waterberg has the largest portion of the Sour Bushveld veld type (De Klerk,
2004). De Klerk (2004) further states that deep sandy soils alternated by shallow and
rocky soils occur on the flats and plateau, while in the valleys the vegetation changes
from riparian vegetation amongst others riparian woodlands and near-forests, reed
beds and marshes/vleis to the predominantly thornveld on the loamy alluvial valley
floors. Apart from the termitaria patches on the slopes, where near-forests develop,

17. 6
there is a great a great wealth of forbs and bushy plants, including stragglers of the
southern (fynbos) flora.
According to Bredenkamp et al. (1996), trees like Silver Clusterleaf Terminalia
serica, Yellow Pomegranate Rhigozum obovatum, Wild Rasin Grewia flava, and
Acacia tortilis are the dominant vegetation in sandy areas. The herbaceous layer, on
the other hand, is usually characterized by grasses such as Broom Grass Eragrostis
pallens, Kalahari Sand Quick Schmidtia pappophoroides, Hairy Love Grass
Eragrostis trichophora, Brachiaria nigropedata, Loudetia simplex, Aristida strata, and
other Aristida species.
1.3 Problem Statement
Coal is a significant source of the primary energy required by the world’s population,
yet its use has detrimental effects on human health and the environment. South
Africa is the sixth-largest coal producer in the world. Most of South African coalfields,
including the Waterberg coalfield, have been investigated extensively while
researchers have paid little attention to the Sekoko Coal Mine, leading to a lack of
documented information on petrography, mineralogy, and geochemistry of coal
within the Sekoko Coal Mine.
1.4 Justification
This study is important for determining the petrographic and mineralogical
constituents of coal in Sekoko Coal Mine within the Waterberg, which is the next
major coalfield. The goal is to gain a better understanding of the sulphide and
carbonate minerals, as well as trace metal and whole rock geochemistry.
Despite the negative impacts that coal poses on the environment, the study on coal
is important. Coal is the most abundant source of electricity worldwide. It is stated by
the Society for Mining, Metallurgy and Exploration (SME) that currently, coal is
providing more than 36% of global electricity. Other than electricity, coal plays an
important role as an ingredient in products essential for public health.

18. 7
This study focused on the analysis of coal in Sekoko coal mine, with emphasis on its
petrographic, mineralogical and geochemical properties. Coal has significant
economic importance as it is used in the production of various products, including
activated carbon which is utilized in air and water purification filters, as well as in
kidney dialysis machines.
Carbon fiber, a lightweight and durable material used in construction, aerospace,
and sports equipment manufacturing, is also produced from coal. Additionally, coal
can be converted into carbon foam, which has high-performance properties required
in military, industrial, and commercial applications. Silicon metal, another important
element, is obtained from coal and is used in the manufacture of various products
such as lubricants, resins, cosmetics, and machine tools.
1.5 Research Questions
 What is the mineralogical composition of host rocks and coal in the Waterberg
coalfield?
 What are the sulphides and carbonate minerals within coal at the Waterberg
coalfield?
 What is the whole rock geochemistry of host rocks and coal in the Waterberg
coalfield?
1.6 Objectives
1.6.1 Main Objective
The main objective of this research was to determine the mineralogical composition
of host rocks and coal in the Waterberg coalfield (Sekoko Coal mine).
1.6.2 Specific Objectives
The specific objectives of this study were to;
 Investigate the mineralogical composition of host rocks and coal in Sekoko
coal mine using petrographic microscopy;
 Investigate the sulphide and carbonate minerals in coal and interburden using
x-ray diffraction method and

19. 8
 Determination of the whole rock geochemistry of coal and interburden using x-
ray spectrometry method.

20. 9
CHAPTER TWO: LITERATURE REVIEW
This chapter focused on the literature search to review the previous work conducted
relevant to the study area and research topic.
2.1 Regional Geology of South African Coalfields
The Karoo is a semi-arid region, located in the southeast in the southern Africa, and
contains the thickest and complete stratigraphic sequence among the Late
Carboniferous to Early Jurassic aged basins that formed in Gondwana (Johnson et
al., 1996). The main Karoo Basin (MKB) of South Africa covers some 300,000 km2
and represents about 120 Ma of sedimentation spanning from about 300 to 120 Ma.
The Karoo rocks covers two-third of the area of South Africa (Geel et al., 2013).
Thomas (2013) further explained that the MKB extends for 200 km from Free State
province west to south and 400𝑘𝑚 from Mpumalanga in the north to KwaZulu-Natal.
The coal deposits of South Africa are found in a series of basins situated in the north
and east of the country (Thomas, 2013). The Karoo basins of South-Central Africa
evolved during the first-order cycle of supercontinent assembly and breakup of
Pagea, under the influence of two distinct tectonic regimes sourced from the
southern and northern margins of Gondwana. (Catuneanu et al., 2005).
According to Snyman and Botha (1993), all of the coal deposits in South Africa are
located in the Karoo Supergroup. Daniel et al. (2019) stated that the abundance of
coal in the Ecca Group was a result of a marshy or paludal depositional environment,
and these coal deposits are only found in the northern part of the basin, with none in
the southern part. However, almost all of South Africa's coal resources are still found
within the Ecca Group. In the Lower Permian Vryheid Formation and the Triassic
Molteno Formation, there are also coal seams present in this southern hemisphere
basin (Cadle et al., 1993).
The Main Karoo Basin (MKB) is part of a significant group of Gondwana basins that
emerged from subduction, compression, collision, and terrane accretion along the
southern border of Gondwana. It is a significant coal-bearing area in South Africa,
and there are also similar-aged coal-bearing strata to the north in isolated

21. 10
extensional intercratonic and intracratonic grabens or half-grabens. The MKB is
renowned as the source of Southern African coal and hosts substantial coalfields in
the region (Cole, 1992; De Wit and Ransome, 1992; Malaza, 2013; Cadle et al.,
1993).
Thomas (2013) elucidated that Verreniging-Sasolberg and South rand coalfields are
found in the western part of the MKB and they consist of coal seams which range
between the thicknesses of 10 to 25 metres. Witbank, eastern Mpumalanga and
Highveld coalfields on the other hand are confined in the northern part on the MKB
and they host five coal seams of which 2 up to 10 m are already worked. The
remaining Vryheid and Utrecht coalfields found in the southern Kwazulu-Natal area
hosts five coal seams, two of which are worked. Thomas (2013) further explained
that there are other coalfield basins in the northeast of the country which are less
developed, and amongst these coalfileds, the Waterberg and the Springbok flats
area appear to have a future potential for coal mining.
Uys (2009) states that the Karoo Supergroup is made up of the Dwyka, Ecca,
Beaufort, and Drakensberg Groups, as well as the Molteno, Elliot, and Clarens
Formations. The changing climatic conditions, as Gondwanaland drifted towards the
equator from high latitudes, are revealed by the paleo-environmental settings of the
Karoo Supergroup, according to Tankard et al. (2009). The conditions range from
partially marine and glacial in the Dwyka Group, to marine in the Ecca Group, and
then to fluvial and Aeolian in the overlying Beaufort and Stormberg Groups,
respectively (Johnson, 1976).
Dwyka Group
The Dwyka Group is up to 800 m thick in the MKB and consists of rocks that display
glacial or glacially-related features and includes diamictites, conglomerates,
fluvioglacial pebbly sandstone and rhythmite (Mtimkulu, 2009). The Group was
named for an exposure along the Dwyka River east of Laingsberg, South African by
Dunn (1875). This confirms what Hancox and Gotz (2014) state that the group was
formed by glacial deposition that took place under high water table conditions which
was marked by the presence of glacial or periglacial lakes. According to Johnson et

22. 11
al., (2006) the Dwyka in the MKB rests on Precambrian bedrock surfaces along the
northern basin margin, in the south it overlies the Cape Supergroup uncomformably
or paraconformably, while in the east it unconformably overlies the Phanerozoic
Natal group and Msikaba Formation.
Ecca Group
Catuneanu et al. (2005) stated that coal is by far the major economic deposit
contained in the Ecca Group. Mtimkulu (2009) further explained that the Ecca Group
hosts the major coal-bearing horizons, namely the Grootegeluk and the Vryheid
Formations and according to Faure et al. (1996), the vast majority of coal beds in
South Africa occur in this Group. In the type-Karoo Basin of South Africa, the Ecca
Group occurs between the Late Carboniferous Dwyka Group and the Late Permian
time slot for Karoo Supergroup lithologies (Catuneanu et al., 2005) but the absolute
age of this Group is not perfectly constrained, and most age determination and
correlations rely on fossil wood biostratigraphy (Bamford, 2004).
According to Hancox and Gotz (2014), there are multiple studies that indicate the
Ecca Group can be divided into various informal units based on the cyclic
sedimentary deposits. The South African Committee for Stratigraphy (SACS, 1980)
officially named the lithostratigraphic units of the Ecca Group in the northern distant
sector of the MKB in 1980. This new naming scheme replaced the previously used
informal divisions of Lower, Middle, and Upper with the Pietermaritzburg Shale
Formation, Vryheid Formation, and Volksrust Shale Formation.
Pietermaritzburg Formation:
The Pietermaritzburg Formation consists of a coarsening-upward sequence of
prodelta siltstones with inter-bedded glaciogenic debris flow and debris rain deposits
that accumulated after a major transgression of the shoreline (Beukes, 1985).
According to the SACS, (1980) this predominantly shale formation attains a
maximum thickness of over 400 m. Uys (2009) further explained that it has the
gradual upper contact where the sandstone/shale ratio is greater than 0.5. The
Pietermaritzburg formation doesn’t host any coal seams (Hancox and Gotz, 2014).

23. 12
Vryheid Formation:
According to Mphaphuli (2017), the coal that can be extracted most profitably is
found in the Vryheid Formation of the Ecca Group. Hancox and Gotz (2014) also
affirmed that the majority of economically viable coal in South Africa can be found in
this formation. The Vryheid Formation consists of four coal seams, ranging from
zone 1 to 4, and it’s strata has a total thickness of 18 m, as described by Roux
(2004). Hancox and Gotz (2014) noted that the thickness of this Formation varies
between 70 meters and over 500 meters within the MKB.
The Vryheid Formation is said to have the highest potential of being an acid
generator which may be due to the dominance of pyrite that is usually found in
sandstone and coal samples (Aphane and Vermeulen, 2015).
Volksrust Formation:
The Volksrust was formerly known as the upper Ecca group before the change of
name by the South African Committee for Stratigraphy. This formation comprises
some 150–250 m of dark siltstone or mudstone (SACS, 1980). Hancox and Gotz
(2014) also state the general thickness of this formation to be 150–250 m, where
coal occurs with the mudstones and the formation itself being postulated to have
formed in shallow-deep water basinal conditions.
Beaufort Group
According to Turner (1981), the Beaufort Group is situated on top of the Ecca Group
in a conformable manner, and the transition between the two groups is characterized
by a gradual shift from a deltaic depositional system to a fluvial depositional system.
This observation supports the claim made by Rubidge et al. (2000) that the Beaufort
Group represents a transitional phase from subaqueous (Ecca Group) to fully sub-
areal deposition with predominantly fluvial sedimentation. The Beaufort Group is
primarily composed of terrestrial deposits, which alternate between arenaeous and
argillaceous sediments. This is in contrast to the predominantly marine deposits
found in the Ecca Group, as noted by Rubidge et al. (2000).

24. 13
This group covers the largest area, more or less 200 000 𝑘𝑚2, in Karoo basin and
reaches a maximum thickness of 6000 m in the Eastern Cape Province (Catuneanu
et al., 2005). Deposition took place in an enclosed foreland basin, of which the east-
west axis migrated considerably farther northwards, compared with that of the partly
enclosed inland sea in which the Ecca Group was deposited.
Keyser and Smith (1979) divided the Beaufort Group into two formations: the
Abrahamskraal Formation and the Teekloof Formation. The Abrahamskraal
Formation is differentiated from the Teekloof Formation primarily by the presence of
chert bands, more numerous sandstones, and a lack of red mudstone. Additionally,
Hancox and Gotz (2014) noted that the Beaufort Group is further subdivided into the
Lower Adelaine and Upper Tarkastad. Coal deposits are only found within the
Adelaine Group.
Stormberg Group
Stormberg Group is the name assigned to the sedimentary geological formations of
the Late Triassic to Jurassic Period, found in the southern Karoo basins (Chima et
al., 2018). Chima et al. (2018) further indicated that the Stormberg Group is an
informal stratigraphic division name, which is made up of three formations, namely,
Molteno, Elliot and Clarens Formations.
Molteno Formation:
According to Turner (1975), the Milteno Formation, which was formed during the
Triassic period, was deposited within braided river channels and gave rise to
conglomerates, sandstone, shale, mudstone, and coal seams. Chima et al. (2018)
further divided the Molteno Formation into three members: the basal Boesmanhoek
Member, the Indwe Sandstone Member, and the upper Kramberg Member.
According to Hancox (1998) there are three coal seams that are present in the
Bamboesberg member.
Turner (1975) and Cairncross et al. (1995) stated that within the MKB, the Molteno
Formation is seen as a northerly-thinning (maximum thickness 640-600 m),
intracratonic, bedload-dominated fluvial wedge deposit, sourced from tectonically

25. 14
active provenance areas to the south and southeast. According to Turner (1975) and
Christie (1981), the Molteno formation forms the basal unit of the stormberg group
and comprises of northward twinning wedges of clastic sedimentary rocks.
Eliot Formation:
The lower part of this formation shows deposition occurred under perennial,
moderately meandering fluvial styles whereas the upper part shows evidence of
ephemeral fluvial processes (Hancox and Gotz, 2014). The Elliot Formation that
overlies the Molteno Formation comprises of lateral continuous floodplain mud-
stones and associated fluvial sandstones (Chima et al., 2018). The sandstones of
the Elliot Formation according to Bordy et al. (2004) are often coarse and gritty at the
base, very persistent and also calcareous. Hancox and Gotz (2014) indicated that
this formation does not host any coal deposit.
Clarens Formation:
The Clarens Formation is the youngest sedimentary deposit in the Karoo Basin
(Chima et al., 2018). Chima et al. (2018) further stated that this formation overlies
the Elliot Formation and it represents the final stage of aridification process. The
Clarens Formation consists of sandstones and sandy siltstones formed from
14eolian processes (Johnson, 1976). Halzförster (2007) and Eriksson et al. (1994)
stated that most authors are in accord on that the sandstone dominated deposits of
the Clarens Formation represent 14 eolian depositional systems, with minor fluvial
input. Hancox and Gotz (2014) also indicated that there is no coal deposit in this
formation.
2.2 Local Geology
The Waterberg Coalfield is characterised by an upper 60 m thick sequence of
intercalated mudstone and coal bands (Grootegeluk Formation), with a lower 55 m
thick portion of discrete seams (Vryheid Formation) more similar in character to the
seams occurring in the Central Basin (Jeffrey, 2005). The major coal-bearing
horizons are the Grootegeluk and the Vryheid Formations and are both found in the

26. 15
Ecca group (approx. 280 Ma) of the Karoo Supergroup together with the
Goedgedacht Formation (Mtimkulu, 2009).
Grootegeluk Formation:
The Grootegeluk Formation (Fig. 2.1) is economically the most important unit of the
Karoo Supergroup, as it contains a number of thick, mineable coal seams (Fourie,
2008). The Grootegeluk Formation in the Waterberg Coalfield consists of coal and
mudstone layers that were deposited during the late Permian, in a basin that
developed on the ancient Limpopo Mobile Belt (Faure, 1993). The deposition of this
formation is considered to have occurred in a period of basin infilling and poor
drainage resulting in the deposition of a 100 m thick interlayered coal and mudstone
succession (Mtimkulu, 2009). According to Faure (1993), it is evident that the
thickness of the Grootegeluk Formation changes laterally where the base of the
formation is 70 m below the topmost coal seam at the GCM and it is 23 m below at
Draai Om.
Vryheid Formation:
Mphaphuli (2017); Hancox and Gotz (2014) emphasized that the Vryheid Formation
within the Ecca Group contains the most economically viable coal and that the
majority of South Africa's economically extracted coal is found in this Formation.
According to Faure et al. (1996), the coal seams in the Vryheid Formation are
primarily composed of dull coal with some carbonaceous mudstone intercalations.
The Formation consists of both coarsening-upward deltaic cycles and fining-upward
fluvial cycles, as noted by Mtimkulu (2009). Additionally, Bordy et al. (2002) stated
that the fluvio-lacustrine deposits of the Basal Unit in the Vryheid Formation, which
contain coal, are similar to the deposits found in the fluvial interval.
Goedgedacht Formation:
Faure (1993) suggested that mudflows, which are primarily found in the northern part
of the basin, were likely the result of glaciers retreating to the north. Siepker (1986)
proposed that these mudflows be referred to as the Goedgedacht Formation.
Mtimkulu (2009) described the Goedgedacht Formation (Fig. 2.1) as consisting of

27. 16
mudstone units with graded bedding and angular quartz grains ranging from sand to
pebble sizes in their lower sections. These units may be topped with thin layers of
impure coal containing vitrinite. Overall, the formation includes multiple beds of
mudstone with graded bedding, some of which are capped with impure coal, as
noted by Fourie (2008).
Figure 2.1: Geological map of the study area (Data source: council for geoscience).
2.3 General Overview of Prominent South African Coalfields
Hancox and Gotz (2014) identified the most significant coalfields in South Africa,
which are located in the Highveld, Waterberg, and Witbank provinces (Fig. 2.2).
There are 19 recognized coalfields in South Africa based on factors such as coal's
origin, formation, distribution, quality, and sedimentation (Hancox and Gotz, 2014).
The majority of South Africa's coal was generated during the Permian period, with
differences in sedimentation, origin, formation, distribution, and quality contributing to
the variation of coal across the country (Mphaphuli, 2017; Hancox and Gotz, 2014).
Bituminous coal is predominant in South Africa, with some anthracite deposits found

28. 17
in the KwaZulu-Natal coalfields (Mphaphuli, 2017). Coal in South Africa is used for
electricity production, manufacturing synthetic fuel, and metallurgical processes
(Hancox and Gotz, 2014).
Preserved coal can be found in rocks from the Karoo Supergroup in South Africa.
The Karoo Supergroup comprises four groups, namely the Dwyka, Ecca, Beaufort,
and Stormberg groups. The Vryheid Formation in the Ecca Group contains the most
commercially viable coal (Mphaphuli, 2017).
Figure 2.2: Coalfields of South Africa (Hancox and Gotz, 2014).
2.3.1 Witbank Coalfield
The Witbank coalfield is situated east of Johannesburg in the Mpumalanga province
(Pinetown et al., 2007). It spans an area of approximately 568000 ha, with a length

29. 18
of 90 km in the West-East direction and 50 km in the North-South direction (Hancox
and Gotz, 2014). According to Hancox (2016), more than half of South Africa's
saleable coal is produced from the Witbank coalfield, which has been commercially
explored for more than 125 years. This information aligns with Jeffrey's (2005)
assertion that the Witbank Coalfield is the largest-producing and most extensively
documented coalfield in South Africa. The Witbank Coalfield’s coal seams are
typically flat-lying, with a 1 to 3 degree regional dip (Hancox, 2016). These seams
vary in thickness from 0.5 to 6 meters (Chabedi, 2013).
2.3.2 Highveld Coalfield
In Mpumalanga province, the Highveld Coalfield is located next to the Witbank
Coalfield. The coalfield covers over 7000 km2 of land. The coalfield is 95 kilometers
wide from Davel to Nigel, and it is 90 kilometers long from Kriel to Standerton. The
Highveld Coalfield is South Africa’s second-largest coalfield (Hancox and Gotz,
2014). The majority of the rocks that make up this coal field are sedimentary rocks.
There is proof that the pre-Karoo glacial valleys were in charge of the plant
deposition (school of mining engineering, undated). The coalfield consists of five coal
seams, which are part of the Vryheid Formation and are hosted by the Ecca group
sediments of the Karoo Supergroup (Jeffrey, 2005).
2.3.3 Soutpansberg Coalfield
The Soutpansberg coalfield extends 190 kilometers from Waterpoort in the Kruger
national park easterly, south of the province of Limpopo (Dreyer, 1991). Mopani,
Tshipise, and Venda-Pafuri are the three portions or subbasins that make up the
coalfield (Malaza, 2013). Geological features such faults and dolerite inclusions
disturb the coal in this field, with dull coal filling the bottom of the multi-seam in the
Waterpoort area and the top portion of the lower seam on the opposite side of the
Tshikondeni area (Chabedi, 2013). The primary coal seams in the Soutpansberg
Coal Basin are the upper (or main fault) seam and the lower seam. The two seams
run from east to west between major faults, and are divided by a vertical trench that
spans 95 m. This separation is due to the lack of marine sedimentation in the area,
as noted by Hancox and Gotz (2014).

30. 19
2.3.4 Waterberg Coalfield
This coalfield is situated in South Africa’s western Limpopo Province about 25 km
outside of Lephalale town. While it is smaller than other coalfields in terms of surface
area, it is larger in terms of coal seam thickness which is about 110 meters. It has
been named as South Africa’s most notable coal basin, coming in second to the
Witbank and Highveld coalfields (Wheeler, 2015). Both the Vryheid Formation and
the Grootegeluk Formation have coal zones. Most of the coal in the Vryheid
Formation is characterized as dull, while the coal found in Grootegeluk has a bright
appearance with some occurrences of organic mudrock.
The Waterberg coalfield is highly faulted (Fourie et al., 2009). The more recent
Daarby Fault cuts across the Waterberg coalfield dividing the coalfield into a shallow
deposit minable on the surface and the other deep minable underground. According
to Bester and Vermeulen (2010), coal bearing rocks in this coalfield are bounded by
the Limpopo Mobile Belt to the north and the Eenzaamheid and the Ellisras faults to
the north.
2.4 Mining History
Waterberg coalfield has a 75 billion tonnes resources, and is said to host 40% of the
South Africa’s remaining coal resource hence it is regarded as SA’s future as far as
coal is concerned (Moumakwa, 2009). Four main products are mined, includingsemi-
soft coking coal and PCI coal for the local and export market, while power-
generation coal is delivered to nearby Matimba power station (Jeffrey, 2005).
After the discovery of coal in the Grootegeluk farm and intense exploration that was
conducted by the Iron and Steel Corporation, it was then in 1957 that the ISCOR
obtained the surface rights to six farms, Grootegeluk farm included, and work on the
Grootegeluk Coal Mine commenced in December 1974. The Grootegeluk mine was
approved for opening by the ISCOR board in February 1974 after a feasibility study
yielded positive results, according to Alberts (1982).
Sekoko coal mine is a company owned by black South Africans that is presently
mining coal in the Waterberg Coalfield near the Exarro coal mine operated by

31. 20
Grootegeluk. Exarro is mining different coal zones or benches in Grootegeluk, which
are classified into two groups: the Grootegeluk Formation containing shiny coal with
mixed-in shale and the Vryheid Formation composed of dark coal, sandstone, and
carbonaceous shale. (Moumakwa, 2009; Sekoko coal, 2011; Mining Review Africa,
2021).
The Waterberg Coalfield has only had four prospecting shafts, and no underground
mining has been conducted there except for those. Moumakwa (2009) stated that
slightly more than 60% of the remaining coal reserves in the Waterberg would need
to be extracted through underground mining. Conventional truck-and-shovel
methods are employed for mining, although there is a variation in the extraction of
the upper and middle Ecca zones. The upper Ecca is mined in bulk, while the middle
Ecca zones are selectively mined.
According to Moumakwa (2009), Grootegeluk coal mine generated 18.5 million tons
of coal in 2007, with about 14.6 million tons sold to Eskom, roughly 0.72 million tons
exported, and the rest of about 3.18 million tons was sold within the country to
various industries including metals.
Sekoko coal (2011) indicated that Eskom is the existing customer. Coal produced
from Sekoko coal mine is sold to Tutuka and Majuba power stations located in
Mpumalanga province. Mining Review Africa (2021) indicated that Sekoko coal mine
will also supply Matimba power station with coal. Sekoko contains enough coal to
produce 120 mt of coal suitable for metallurgical and thermal export markets.
2.5 Coal Petrology
Microscopic analysis can help identify the constituents of a material, such as coal,
and is often combined with techniques like x-ray diffraction to identify minerals
(Vorres, 1986). Examining coal under a microscope can help to identify its organic
and mineral components and determine its suitability for industrial use, according to
Thomas (2013). Coal consists of various organic constituents called macerals and
microlithotypes, which can be distinguished through microscopic analysis (Faure,
1993).

32. 21
Speight (2015) explained that optical microscopy is a technique utilized to identify
mineral distribution in coal. This method involves the examination of thin or polished
sections of coal using transmitted and/or reflected light under a microscope. By
observing the optical features of coal such as reflectance, morphology, refractive
index, and anisotropy, it is possible to identify the types of minerals present in the
coal.
Macerals
Meyers and Attar (1982) stated that coal is composed of organic materials known as
Macerals, which are remnants of plant matter. These Macerals have different
properties and can be used to determine the quality of the coal (Schweinfurth, 2009).
Macerals are analogous to minerals in coal and are descriptive of the different
organic constituents present in coal (Phupheli, 2007).
The characteristics of minerals that set them apart from one another include color,
polishing hardness, shape, and reflectance. Exinite (liptinite), Inertinite, and Vitrinite
(Table 2.1) are the three classes of macerals that may be distinguished based on
chemical composition and optical reflectance. McCabe (1984) indicated that the
classification of maceral group is referred to as stopes-heerlen system.
Vitrinite:
The most prevalent type of coal, vitrnite, is created when structureless plant
components degrade and coalize. The term "pure coal" is often used to describe
vitrinite due to its tendency to become denser, harder, and more glass-like as it is
subjected to high temperatures from either being deep underground or from the heat
of igneous intrusions (Schweinfurth, 2009). Additionally, according to Scott (2002),
these macerals were quickly deposited in swaps, which reduced the primary
oxidation during coalification. In high-rank coal, vitrinite is difficult to distinguish from
other macerals (Mphaphuli, 2017). Taylor et al., (1998) indicated that the carbon
content in vitrinite macerals is proven to increase consistently with increasing rank.
As such vitrinite is used as a universal standard to measure the reflectance levels of
coals for determination of rank (Gray et al., 1976).

33. 22
Vitrinite:
The most prevalent type of coal, vitrnite, is created when structureless plant
components degrade and coalize. The term "pure coal" is often used to describe
vitrinite due to its tendency to become denser, harder, and more glass-like as it is
subjected to high temperatures from either being deep underground or from the heat
of igneous intrusions (Schweinfurth, 2009). Additionally, according to Scott (2002),
these macerals were quickly deposited in swaps, which reduced the primary
oxidation during coalification. In high-rank coal, vitrinite is difficult to distinguish from
other macerals (Mphaphuli, 2017). Taylor et al., (1998) indicated that the carbon
content in vitrinite macerals is proven to increase consistently with increasing rank.
As such vitrinite is used as a universal standard to measure the reflectance levels of
coals for determination of rank (Gray et al., 1976).
Liptinite:
Liptinite maceral group is also referred to as exinite. This maceral is derived from
hydrogen rich plant organs such as algae, spores and resin (Studer, 2008; Taylor et
al., 1998). When heated, liptinite group yields much more volatile matter compared
to other maceral groups. Liptinite exhibit a lower reflectance as compared to the
vitrinite maceral group (McHugh et al., 1991) and its reflectance increases with the
increase of coal rank (Mphaphuli, 2017). This maceral is not common in South
African coals, it only constitutes 5% (Tlou-Sebola, 2018).
Inertinite:
The inertinite maceral group is produced when plant components that are heavily
changed and degraded during the peat stage of coal generation. The same type of
plant material that goes into making vitrinite also goes into making inertinite maceral
group, although they are more sensitive to variable degrees of partial burning and
oxidation (Mphaphuli, 2017). Fusinite, semifusinite, funginite, macrinite, secretinite,
inertodetrinite, and micrinite are the subgroups of the inertinite group. According to
Thomas (2013), coals can include between 5 and 10 percent fusinite, and fusinite-
rich coals are assumed to be the result of the onset of aerobic conditions during
peat

34. 23
formation. Inertinite macerals’ chemical and physical properties don’t alter all that
much when coal rank increases (Phupheli, 2007).
Table 2.1: Macerals and maceral group description of coal (McCabe, 1984)
2.6 Coal Mineralogy
Speight (1994) defines coal as an organic sedimentary rock that contains varying
amounts of carbon, hydrogen, nitrogen, oxygen, and sulphur as well as trace
amounts of other elements including mineral matter. Akinyemi (2011) highlighted that
geology of the surrounding environment of the coal deposit affects the coal’s
mineralogical constituents. Vorres (1986) also stated that the type of mineral matter
found in a particular deposit depends on the geography of the deposit.

35. 24
Vorres (1986) noted that coal contains a significant amount of mineral matter that
can vary widely. Mineral matter refers to the inorganic components of coal that are
not part of the organic substance, as explained by Speight (2015). Ward (2002)
stated that mineral matter is a result of the peat accumulation process and
subsequent processes. The mineral matter in coal is classified into two categories
based on its origin, as described by Govender (2005): intrinsic inorganic matter that
was present in the original plant tissues, and extrinsic or induced forms of mineral
matter that can be primary or secondary. Vorres (1986) also indicated that the
mineral matter in coal includes the mineral matter present in the living plants which
were altered over time to produce the coal material.
Jenkins and Walker (1978) stated that there are several sources of mineral matter
found in coals. First, there is inorganic material generated from the plants which form
the coal swamp. Jenkins and Walker (1978) further explained that inorganic
compounds were introduced from outside sources by mechanisms such as erosion
either into the decaying vegetation or, at a later stage, into the coal seam by
percolation through cracks or fissures.
According to Speight (2015), mineral matter in coal is generally categorized as
inherent or adventitious mineral matter. Inherent mineral matter refers to organic
material that is closely linked to the coal substance and cannot be easily separated
using current methods. In contrast, adventitious mineral matter refers to inorganic
materials that are less closely associated with coal and can be separated more
easily. Thomas (2013) explained that these minerals are either detrital or authigenic
in origin and are introduced into the coal during the first and second phases of
coalification.
According to Thomas (2013), detrial minerals are those transported into the swamp
by water or wind and authegenic minerals those that are introduced into the peat
during and/or after deposition. Thomas (2013), Vassilev and Vasilev (1996) further
stated that different minerals that occurs in coal includes quartz, carbonate, iron and
clay minerals where clay minerals make up between 60 to 80% of the total mineral
matter associated with coal.

36. 25
Speight (2015) stated that mineral matter in coal is generally regarded as
unfavorable and harmful for coal utilization, and its presence affects virtually all
aspects of coal mining, preparation, transportation, and utilization. Jenkins and
Walker (1978) explained that in coal mining and transportation, mineral matter acts
as a diluting agent and is therefore considered undesirable.
2.7 Environmental Impacts of Coal
Coal is one of the most essential and abundant types of rocks used today. With the
composition of carbon, coal is mainly used as fossil fuel to produce electricity and
heat and as of the present, coal is one of the world’s major sources of power
generation (Song et al., 2010). Coal plays a significant role in global energy
production but has a notable environmental impact. Bell et al. (2001) state that the
severity of the environmental impact of coal mining depends on several factors, such
as whether the mine is operational or abandoned, the mining technique employed,
and the geological conditions.
Goswami (2015) stated that activities that may degrade the land, water, air and
subsequently the quality of life include improper disposal of coal wastes or coal
mining activities. To utilize coal as an energy source, it is necessary to address the
environmental issues related to coal and coal mining, which may include but are not
limited to problems such as land subsidence, water pollution, air pollution, spoil
heaps, acid mine drainage, and disruption of hydro-geology (Zhengfu et al., 2010).
The burning of coal releases harmful substances such as sulphur dioxide, nitrogen
oxide, carbon dioxide, as well as particulates of dust and ash (Goswami, 2015). The
emission of CO, CO2, NOx, Sox happens because of spontaneous coal combustion
and methane leaking from coal strata and coal seams (Zhengfu et al., 2010). Coal
mining does not only affect the local environment but also affects the global
environment through the release of coal bed methane (Goswami, 2015).
The leakage of methane, carbon dioxide and other types of greenhouse gases in an
attempt to recover this coal from the ground is affecting the world’s atmosphere with
global warming (Coal, 2022). The emission of methane from coal mining depends
on various factors such as the mining method, coal quality, depth of coal mining, and
the gas content trapped within the coal seam. Methane is a greenhouse gas that has

37. 26
a greenhouse effect 21 times more potent than carbon dioxide (Zhengfu et al.,
2010).
Coal and coal mining can impact negatively on water environment. According to
Zhengfu et al. (2010), the mining of coal has an impact on the water environment
through various mechanisms. These include a decrease in the water table due to
mining activities, resulting in water loss or pollution. Additionally, alterations to
watercourses can occur. The exposure of previously unexposed minerals can result
in reactions with gaseous or liquid components in the new environment, which can
lead to contamination of water. As a result, water chemistry and aesthetics can be
affected, and the level of suspended solids in water can increase (Zhengfu et al.,
2010).
Breaking of coal and leaching pyrite (of sulphur content) from the coal and
surrounding formation leads to Acid Mine Drainage (Goswami, 2015). According to
McGinnes (1999) AMD occurs as a result of oxidation of sulphides when exposed to
water and oxygen, and sometimes due to biological reactions caused by bacterial
activities. When pyrite is enclosed within a rock, only minimal amounts of pyrite are
oxidized through natural weathering, thereby generating only small amounts of acid.
When fully exposed to air and water, the chemical reactions forming AMD occur at a
faster rate (Mitchell and Craddock, 2022).
The problem with AMD is that it lowers the pH of water resulting in the water being
acidic and if not controlled, this water may be drained towards surrounding water
bodies and temper with their water pH. After having retained the low pH, water is
therefore not suitable for use by animals, plants, mankind and aquatic life (Riley et
al., 1972). These problems are not restricted only to the lifetime of the mine but can
continue even after the life of the mine (Kumari, et al., 2010).
2.8 Stratigraphy of the Waterberg Coalfield
Hancox and Gotz (2014) provided a description of the stratigraphic sequence found
in the Waterberg sub-basin, stating that it is composed of a late Palaeoproterozoic
metaconglomerates and metaquartzites of the Waterberg Group, which is part of the
Transvaal Supergroup. According to Johnson (1996), the key difference between the

38. 27
main Karoo Basin and smaller basins in South Africa is the presence of finer non-
fluvial sediments in the northern basins, which indicates lacustrine rather than open
shelf conditions. However, all the recognized lithostratigraphic units of the Karoo
Supergroup in the Main Basin are present in the Waterberg basin (Beukes, 1985).
The number of coal seams in the Waterberg Coalfield is greater than in other
coalfields, which typically have only five seams within the Vryheid Formation. The
Waterberg Coalfield has been found to have a total of 11 coal seams, four of which
occur within the Vryheid Formation, and the remaining seven within the overlying
Grootegeluk Formation (Hancox and Gotz, 2014). According to Faure et al. (1996),
the Vryheid Formation is made up of zones 1 to 4A and 4, which mainly comprise of
sandstone, coal, shale, siltstone, mudstone, and grit, with some Dwyka tillite present.
Coal seams are mainly present in zones 5 to 11, which are mostly composed of coal
interbedded with shale, siltstone, and mudstone (Mtimkhulu, 2009).
In the Waterberg Coalfield, the Vryheid Formation is characterized by sandstones
and coal seams that are predominantly dull. Originally, the Ecca Group in the
Waterberg Coalfield was divided into various zones from the bottom up, including
zones 1, 2, 3, 4A, 4, 5A, 5B, 5C, 6A, 6B, 6C, and 7, as outlined by De Jager (1976).
However, most authors have accepted a numbering scheme for these zones, and
the coal found in the overlying Grootegeluk Formation has generally been referred to
as zones 5-11.
Hancox and Gotz (2014) state that Zones 1 to 4 contain predominantly dull coal with
brighter coal present at the base of each seam. At Grootegeluk, Zone 1 is described
as a dull coal seam measuring 1.55 m in thickness with a small number of bright
layers and some slim mudstone intercalations. According to Hancox and Gotz
(2014), the different zones in the Waterberg Coalfield can be described as follows:
Zone 2 is 3.73 m thick and consists of a dull coal, with the lower 2 m producing coal
with lower ash content. Zone 3 is the thickest at 7.82 m. Zone 4 is a composite zone
(4A, interbeds, and 4) that is approximately 10 m thick. However, the lower zones in
the Grootegeluk Formation have limited potential for coking coal. The upper seven
zones (zones 5-11) have similar coal qualities, except for zone 6. The thickness of
this coal zones are also seen in the GCM, coal zone/mining benches (Fig. 2.4). As

39. 28
seen in Fig. 2.3, Mtimkulu (2009) states that zone 4 and 4A seams constitute a clear
transition phase between Ecca and Upper Ecca stages in this field.
Figure 2.3: Stratigraphic column of the geology of the Waterberg Coalfield (Hancox
and Gotz, 2014).

40. 29
Figure 2.4: The Grootegeluk Coal Mine, coal zone/mining benches.
Siepker (1986) describes 11 genetic stratigraphic units otherwise termed Genetic
Units of Sedimentation (GUS). The Grootegeluk Formation (GUS 5) conformably
overlies the Swartrant Formation in the east and extreme south, while in the central
and north areas of the preserved basin, the lower half of the Grootegeluk apparently
interfingers with the Goedgedacht Formation. The formation consist of mudstone,
carbonaceous shale and coal (Mtimkulu, 2009). According to Mtimkulu (2009), the
lower half of the succession in the Waterberg Coalfield is characterized by prominent
coals and highly carbonaceous shales. The complete succession is divided into 38
zones, each containing a variable number of cycles. Zones 1-6 are made up of dark,
highly carbonaceous mudstone and uninteresting coal. Zones 7-28 are composed of
alternating bright and uninteresting coal and carbonaceous shale, while zones 29-38
are characterized by vitrinite-rich bright coal and carbonaceous shale.
Goedgedacht Formation is the equivalent of GUS 4 and according to Siepker (1986)
this formation only prevails over the north and northwest part of the Ellisras basin
Karoo outcrops. Mtimkulu (2009) explained how that the formation decreases from a

41. 30
maximum thickness of 80m in the north, towards the south, where it interfingers with
the Swartrant Formation. According to Mtimukulu (2009), the Goedgedacht
Formation is composed of layers of mudstones that have a graded bedding pattern
and contain angular quartz grains in their lower sections. These layers may also be
topped with a thin layer of impure coal that is rich in vitrinite.
Le Blanc Smith (1980) established a council genetic stratigraphy by identifying ten
widely distributed marker horizons, which allowed for the division of the succession
into 11 Genetic Increments of Strata (GIS). The Waterberg Coalfield is considered
to be GIS 6, and several authors associate it with the Volksrust Formation in the
MKB. Dreyer (2011) also utilized the Volksrust Formation to refer to the sedimentary
deposits containing the upper coal zones, as noted by Hancox and Gotz (2014). The
coal deposits found in the Grootegeluk Formation in the Waterberg Coalfield are
characteristic of the thick interbedded seam deposit type as defined in SANS 10320
(2004).
2.9 Laboratory techniques
The analysis of coal can be done using x-ray spectroscopy, x-ray diffraction, x-ray
absorption spectroscopy, electron microscopy, scanning electron microscopy,
electron probe microanalysis, atomic spectroscopy, and atomic absorption
spectroscopy (Zhu, 2014). For the purpose of this research, the following methods
were used, x-ray fluorescence, x-ray diffraction, and petrographic microscopy.
X-Ray Diffraction:
A powerful non-destructive method for characterizing crystalline and polycrystalline
materials is X-ray diffraction (XRD). It gives details on structures, phases, and
optimum crystal orientations (Aboul-Enein, 2015). These tools are essential for
mineral exploration and an important component of geological research. According
to Aboul-Enein (2015), powdered samples must be dominantly fine (45 m) for XRD
analysis in order to prevent spottiness.
According to Zhu (2014), the best approach currently available for identifying mineral
phases and minerals in coal is XRD analysis. It is a potent analytical tool for

42. 31
identifying and characterizing coal's unknown mineral matter
composition (Zhu, 2014). Coal is subjected to polycrystalline diffraction examination.
All XRD techniques are based on producing x-rays in an x-ray tube, directing these
rays at the sample, then detecting and measuring the diffracted rays (Zhu, 2014).
Due to its precision, the XRD was chosen. Zhu (2014) stated that the XRD produces
results that are accurate to within 15% of the actual values.
X-Ray Fluorescence:
X-ray fluorescence operates on the basic principle of the interaction between X-ray
photons from various excitation sources and atoms of the target elements that are
present in the sample (Andrew, 2004). In addition, according to Andrew (2004),
when these excitation photons engage with the sample's atoms, inner shell electrons
are ejected, and the outer shell electrons subsequently fall into the empty spaces,
emitting the element's characteristic X-rays (Andrew, 2004).
According to Andrew (2004), the energy level of a specific X-ray is determined by the
difference in the binding energies of the electron shells involved. The intensity of X-
rays produced at a particular energy level can be used to determine the amount of
the element present by comparing it to standards, since the energy level of the X-ray
is a unique property of the element. A radiation source, a sample chamber, a
detector, and a computer for data processing are common components of a
spectrometer (Fig. 2.5) (Andrew, 2004).
X-ray fluorescence has several shortcomings including, the XRF signal should be
calibrated against known standards and also XRF is less useful for measurements of
elements with low atomic numbers, typically it cannot measure elements with atomic
number less than 11, this is caused by the weak fluorescence from these species
(Andrew, 2004).

43. 32
Figure 2.5: Schematic representation of an X-Ray Fluorescence (Andrew, 2004).
Petrographic Microscopy
The examination of organic and inorganic components in coal is known as coal
petrography, as described by Wagner et al. (2018). Coal petrography, according to
Cloke and Lester (1994), is a fundamental method for characterizing coal and
mineral materials. Petrographic techniques, such as vitrinite reflectance, have
improved the identification of coal type (maceral composition), the association of
macerals and mineral matter in coal (microlithotypes), textural connections between
mineral matter and macerals, and coal rank. The use of petrography has also aided
in the comprehension of coal's origin, formation, development of sedimentary basins,
and depositional environment (Teichmfiller, 1989).
The visible maceral on the crosshair beneath the eyepiece is classified and counted
to determine the relative quantity of macerals present in coal, as outlined by SABS
ISO 7404-part 4. While petrographic studies have provided a better understanding of
coal geology and geochemistry, it is important to acknowledge that the method
requires time and a trained petrographer to analyze the coal (Gluskoter, 1975).

44. 33
Figure 3.1: Flow chart summarising the methods and procedures applied in this study.
CHAPTER THREE: MATERIALS AND METHODS
This chapter presents the methods and procedures that were applied in the study
(Fig. 3.1).
Figure 3.1: Flow chart summarising the methods and procedures applied in this study.

45. 34
3.1 Preliminary Study
Preliminary work mostly refers to the preparatory activities undertaken before the
actual fieldwork. These activities were carried out in order to identify materials and
methods which were necessary to undertake in the study. Information gathered in
this stage provided the knowledge about the study area and any challenges that
were posed to the study. Preliminary work included desktop study and
reconnaissance survey.
3.1.1 Desktop
Desktop study was conducted to gather primary information about the study area's
location, attributes, and ease of access. This information was gathered from various
sources which included, but not limited to books, published and unpublished
documents, records, internet sources, Journals, topographical and geological maps.
The information was collected through intensive literature review which provided the
information about the study area. It also assisted in selection of the best materials
and methods, and entails all the physical demands possessed by the study area.
3.1.2 Reconnaissance Survey
Reconnaissance survey was undertaken so as to be familiar with the immediate
surroundings, demarcating the study area and to conceptualize procedures for
fieldwork. It is crucial to conduct reconnaissance survey as it will help kick-start
planning for fieldwork. During this stage, geological setting, topography, drainage soil
type, and vegetation type were investigated.
3.2 Field Work
This is the backbone of the research work, the component of the research that
ensures that the objectives of the study are achieved. This is the actual work in the
field, a true interaction with the study area.

46. 35
3.2.1 Sample Collection
Host rocks and coal were sampled from the surface coal-bed exposure at the
Sekoko coal mine (Fig. 3.2). Thomas (2012) suggested that channel sampling is a
reliable method for obtaining representative coal samples from a specific location.
Hence, for the present study, the channel sampling technique was employed, and
samples were collected from seam 10 at the box-cut.
The face of the pit was cleared prior to sampling. A scoop was used to form a
uniform channel down the seam to collect a composite sample so as to have a
representative quality of the seam. Different plies of seam 10 were sampled to have
detailed quality of each parting of the seam.
Stockpile sampling was conducted to obtain samples for seam 11. In this case,
stockpile was used because seam 11 was not accessible from the pit. To ensure that
the sample was a representative of the stockpile, four scoops were collected along
each side of the stockpile and two scoops were collected on the top of the stockpile
(Fig. 3.3). All samples were taken after exposing the fresh part by clearing the
outcropping part to prevent collecting oxidised samples.
All samples that were collected were stored in a sampling bag with proper labelling.
The sampling bag was closed tightly such that the coal did not lose its moisture
content, to minimise contamination and oxidation. A total of 18 samples were
collected from the box cut.

47. 36
Figure 3.2: Sampling from the box-cut.
Figure 3.3: Sample collection from the stockpile.

48. 37
3.3 Laboratory work
Laboratory work was conducted both on coal and interburden from the study area.
This involved preparation of samples for different purposes such as preparation for
petrographic and ore microscopic studies for rocks and coal specimen respectively.
Preparation of samples for mineralogical investigation using XRD and preparation of
samples for whole rock geochemistry of both host rocks and coal specimen.
At this stage, analysis of thin-sections and ore blocks prepared was done using
petrographic microscope and coal petrographic microscope respectively. During all
the laboratory activities, quality assurance and control were taken into consideration.
3.3.1 Sample Preparation
Sample preparation involved all the standard procedures followed in preparing
samples for petrographic studies, ore microscopy and whole rock geochemistry.
3.3.1.1 Sample preparation for Petrographic Study of Host Rocks
Thin section and polished blocks were prepared for petrographic study. Host rock
specimens were prepared for thin section while polished blocks were prepared for
coal samples.
Preparation for Thin-Sections
From the samples collected, representative samples were selected and prepared for
thin-sections. This was done following the steps in preparation of thin sections where
host rocks and coal were cut into small sizes using a diamond saw (Fig. 3.4A). The
samples were then trimmed to smaller sizes using Streuers Accutum-50 machine
(Fig. 3.4B) and was then polished using silica carbide grit of different sizes (Fig.
3.4C). The polished samples were then ready for bonding and so they were dried
using Vacutec drying oven (Fig. 3.4D) to remove excess water. In preparation of an
epoxy bonding solution, a ratio of 1:7 was used when mixing hardener and resin
respectively. The solution was then used to bond the samples in a glass slide.
Samples were placed on a bonding jig (Fig. 3.4E) and were left for 24 hours to bond.
Streuers Accutum-50 machine was used to cut and reduce the bonded samples to

49. 38
size. A grinding disc was then used to grind the samples to 50 micrometers. Then
lastly, the samples was polished using a Streuers RotoPol-35 lapping machine (Fig.
3.4F) and diamond solution was used for polishing. A micrometer was used to check
the required thickness of the sample, about 35µm for accurate analysis.
Figure 3.4: Preparation of thin-sections
Preparation for Polished Blocks
A total number of six coal samples were selected for polished block preparation at
the University of Johannesburg. Coal samples were crushed to pass the 1 mm sieve.
Thereafter, bonding material was prepared using a ratio of 1:7 for hardener and resin
respectively. The bonding material was poured into a mounting cup. Subsequently,
the crushed coal was added into the same mounting cup and stirred. Samples were
placed in a vacuum to remove bubbles for 24 hours. Upon drying, polished blocks
were polished using Struers Rotopol 35 PdM-Force-20 (Fig. 3.4F) to achieve a
smooth surface. Polished blocks were placed in a closed container awaiting
petrographic analysis.
3.3.1.2 Sample preparation for Mineralogical analysis using XRD
For the mineralogy of host rocks and coal, samples were prepared for a non-
destructive technique which is x-ray diffraction. Zhu (2014), stated that XRD is a

50. 39
potent analytical method for identifying and analyzing the unknown mineral content
of coal. All XRD techniques are based on generating X-rays using an X-ray tube,
directing them towards the sample, and detecting and measuring the diffracted rays.
Sample preparation was done by crushing a representative sample using a jaw
crusher (Fig 3.5). The sample was then pulverized to homogeneous powder before
XRD analysis using a mechanical Retsch RS 200 milling machine (Fig 3.5A) such
that it passes the 212 µm sieve. Samples were then ashed using Vacutec furnace at
750°C for a period of 2 hours in order to remove the organic materials. 150g of the
samples were sent to an external laboratory for x-ray diffraction analysis. The
samples were prepared for XRD according to the standardized Panalytical
backloading system, which provides a nearly random distribution of the particles.
Figure 3.5: Preparations of samples for X-ray fluorescence spectroscopy.

51. 40
3.3.1.3 Preparation for Whole Rock Geochemistry
The process of whole rock geochemistry involves the identification of both oxides
and trace elements using XRF spectrometry, which can measure periodic table
elements qualitatively and quantitatively in the sample.
Preparations were done at the Department of Earth Science, University of Venda by
milling the samples milled in Retsch RS 200 milling machine (Fig 3.5A) for five
minutes at 700 rpm. The milling pot was cleaned using quartz sand to prevent
contamination prior analysis. The pot was also cleaned using acetone to ensure that
quartz sand did not contribute in the SiO2 content of the samples. Milled samples
were stored and properly labelled.
Copper was used for calibration then the samples were pelletized for x-ray
spectrometry. Samples were palletised by adding sample into pallet cup and boring
acid (Fig 3.5B) was used to bond the sample together. The pallet cup was then
placed in an automatic hydraulic operated pressing machine (Fig 3.5D) were it was
pressed at 30 tons load. The sample was placed on a container with proper labelling.
These steps were repeated for 8 selected samples. Analysis was conducted at the
University of Pretoria.
3.3.2 Sample Analysis
3.3.2.1 Petrographic Study
Microscopic and mineralogical characteristics of both host rock specimens and coal
samples was undertaken. Three host rock specimens underwent transmitted light
petrographic microscopy, whereas six coal samples were studied using organic
petrography. For 8 samples, quantitative mineralogical analyses were conducted (3
rock specimens and 5 coal samples).
According to Craig and Vaughan (1994), the microscopic study of rock specimens
enabled a greater knowledge of its mineral constituents. An Olympus Zeiss AxioCam
transmitted light petrographic microscope (Fig. 3.10) was used for petrographic
analysis at the Department of Earth Sciences, University of Venda. Prior to analysis,
the axis was aligned and the microscope was adjusted. The structure, form, and size

52. 41
of the mineral consituents were examined under transmitted light on a total of three
host rock specimens. These specimens were analyzed at a scale of 200 µm. The
photomicrographs were further interpreted and discussed.
Figure 3.6: Olympus BX51 transmitted and reflected light petrographic microscope
used for petrographic study of rock specimens.
Petrographic study of Ore Samples
Maceral analyses were performed on polished blocks under a reflected light
microscope equipped with an oil immersion objective lens and an automatic point
counting stage that traverses the sample at 0.4 mm intervals in accordance with ISO
7404-3. Under the cross hair, a minimum of 500 points are counted. To calculate the
coal reflectance, an objective lens with a magnification of x50 is used, and the stage
or light path is rotated 360 degrees. A minimum of 100 readings on vitrinite bands
within the measurement area are taken. Vitrinite is used because it has a constant
and linear loss of volatile matter as well as an increase in carbon content (Wagner et
al., 2018). High quality sample preparation is required to ensure good results.
Coal analysis was done using Zeiss Axioimager M2m polarized reflected light
microscope with a 50X oil immersion objective lens and Fossil monochrome and
color cameras were used to analyze coal samples (Fig. 3.11). Professor N. Wagner

53. 42
from the University of Johannesburg's Geology Department provided guidance on
studying the principal groupings, subgroups, and inorganic component of coal. Prior
to analysis, the microscope was calibrated using a yttrium-aluminum-garnet 0.900
disk and immersion oil. For macerals and mineral matter analysis, a 500 point count
was performed, and for vitrinite reflectance, a 100 point count was performed.
Following ISO 7404-3, samples were analyzed, and results were presented as
volume percentages. Results for the maceral point count and the vitrinite reflectance
were tabulated.
Figure 3.7: Zeiss Axioimager organic petrography microscope used for maceral point
count and vitrinite reflectance studies.
3.3.2.2 Mineralogical Analysis of Host Rocks and Coal
To analyze the mineralogy of the host rocks and coal, samples were sent to the
University of Pretoria, where they were studied using a PANalytical X’Pert Pro
powder diffractometer in θ–θ configuration. The instrument was equipped with an
X’Celerator detector and variable divergence- and fixed receiving slits, and Fe
filtered Co-Kα radiation (λ=1.789Å) was used. The mineralogy was determined by
comparing the measured diffraction pattern with patterns in the ICSD database and
selecting the best-fit pattern, using X’Pert Highscore plus software. Wiebke Grote at

54. 43
the University of Pretoria analyzed the samples, and the findings are presented in
Table 3.1.
Table 3.1: Quantitative mineralogy of coal and interburden
Quartz Kaolinite Pyrite Muscovite Microcline Anatase Magnetite Amorphous
PLY_A_F-
R 75.1 23.5 0 0.9 0 0.5 0 0
A_S-L 63.6 22.2 0 3.4 10.5 0.3 0 0
E_S-L 2.6 13.0 6.9 0 0 0 1.0 76.5
H_S-L 3.8 11.8 9.4 0 0 0 0 75.1
SEAM
Comp10 9.4 21.9 1.3 0 0 0 0 67.3
SEAM
Comp11 7.8 25.2 1.1 0 0 0 0 66.0
Shale F-R 36.0 60.5 0 3.0 0 0.5 0 0
C_F-R 4.4 15.3 1.3 0 0 0 0 78.9
3.3.2.3 Whole Rock Geochemistry Analysis
The University of Pretoria conducted the analysis of the samples, which involved
drying and roasting them in alumina refractory crucibles at 100°C and 1000°C,
respectively, to determine their Loss On Ignition (LOI). To create a stable fused glass
bead, a 1g sample was mixed with 6g Lithiumteraborate flux and fused at 1030°C.
Thermo Fisher ARL Perform'X Sequential XRF instrument with Uniquant software
was used to analyze the samples for all elements in the periodic table between Na
and U, but only those elements that were detected were reported. The results were
normalized to include LOI to identify changes in crystal water and oxidation state.
The same procedure was used to prepare and analyze a standard sample material,
and the results for both clastic sedimentary rocks and coal are presented in Table
3.2 and 3.3.

55. 44
Table 3.2: Concentrations of major oxides in clastic sedimentary rocks
Clastic Sedimentary Rocks
Major Oxides
PLY
A-F-R
PLY
A-S-L
SHALE
F-R
SiO2 85.05 85.61 61.63
Al2O3 7.89 8.30 23.48
MgO 0.02 0.02 0.11
Na2O <0,01 <0,01 <0,01
P2O5 0.29 0.06 0.10
Fe2O3 0.44 0.46 0.47
K2O 0.10 1.12 0.40
CaO 0.04 0.03 0.05
TiO2 0.38 0.15 0.95
V2O5 0.01 <0,01 0.03
Cr2O3 0.18 0.07 0.04
MnO 0.02 0.01 <0,01
NiO 0.03 0.01 <0,01
CuO <0,01 <0,01 <0,01
ZrO2 0.20 0.09 0.27
S 0.02 0.01 <0,01
ZnO 0.01 <0,01 0.02
SrO 0.08 0.02 0.04
Y2O3 0.01 <0,01 0.02
LOI 5.22 4.04 12.38
TOTAL 99.99 99.99 99.97

56. 45
Table 3.3: Concentrations of major oxides in coal
West far right of seam 10 South portion of seam 10 Composites
Major
Oxides (Wt
%)
PLY
B-F-R
PLY
C-F-R
PLY
D-F-R
PLY
E-F-R
PLY
F-F-R
PLY
G-F-R
PLY
B-S-L
PLY
C-S-L
PLY
D-S-L
PLY
E-S-L
PLY
F-S-L
PLY
G-S-L
PLY
H-S-L
SEAM
10
SEAM
11
SiO2 11.93 5.92 5.61 24.57 23.39 18.21 5.25 3.37 21.36 6.68 5.65 59.47 5.01 16.09 12.25
Al2O3 6.62 3.26 3.27 12.60 12.76 10.18 3.26 2.00 14.23 4.19 3.09 19.30 2.93 8.90 7.13
MgO 0.00 0.00 0.00 0.04 0.04 0.03 0.00 0.01 0.04 0.00 0.00 0.05 0.02 0.02 0.02
Na2O 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
P2O5 0.02 0.01 0.00 0.03 0.03 0.02 0.01 0.01 0.03 0.01 0.01 0.06 0.00 0.02 0.01
Fe2O3 0.21 1.22 1.43 0.31 0.30 0.39 0.29 0.71 0.39 4.31 0.30 0.33 5.26 0.99 1.31
K2O 0.03 0.03 0.01 0.09 0.08 0.06 0.03 0.04 0.10 0.06 0.03 0.12 0.05 0.07 0.05
CaO 0.01 0.02 0.01 0.01 0.01 0.02 0.01 0.02 0.01 0.02 0.01 0.02 0.03 0.03 0.01
TiO2 0.23 0.21 0.12 0.53 0.47 0.40 0.11 0.10 0.49 0.31 0.14 1.49 0.11 0.36 0.24
V2O5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00
Cr2O3 0.00 0.00 0.00 0.01 0.01 0.01 0.00 0.00 0.01 0.01 0.01 0.01 0.02 0.02 0.01
MnO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00
NiO 0.00 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.00 0.01 0.01 0.00 0.01 0.01 0.01
CuO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
ZrO2 0.05 0.06 0.04 0.13 0.10 0.10 0.03 0.04 0.09 0.05 0.05 0.20 0.03 0.10 0.06
S 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.00
ZnO 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00
SrO 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.01 0.01 0.01
Y2O3 0.01 0.01 0.01 0.02 0.01 0.02 0.00 0.00 0.01 0.01 0.01 0.02 0.01 0.01 0.01
LOI 80.86 89.21 89.45 61.62 62.76 70.52 90.96 93.65 63.22 84.3 90.66 18.89 86.47 73.33 78.87
TOTAL 99.98 99.98 99.98 99.96 99.99 99.97 99.97 99.97 99.99 99.97 99.98 99.98 99.97 99.98 99.99

57. 46
CHAPTER FOUR: RESULTS AND DISCUSSION
The presentation and the discussion of the results are outlined in this chapter. The results are
discussed for stratigraphic sequence, petrographic and mineralogical analysis, and whole
rock geochemistry (X-ray diffraction and X-ray spectrometry)
4.1 Characterisation of Host Rocks and Coal
The petrographic data provides a detailed description of the three clastic sedimentary rocks
and six coal samples from the Sekoko coal mine in the Waterberg Coalfield. The samples
were initially visually inspected by characterizing the physical characteristics of viewable
minerals in order to completely understand them.
4.1.1 Description of Host Rocks
A petrographic microscope with a magnification of 200 was used to examine the minerals'
optical characteristics in each sample.
Shale
Shale (Fig. 4.1) was described in the field as having fine clay-sized particles that were grey in
color. Clastic, argillaceous sedimentary rock makes up the specimen. It is competent, has thin
parallel beds that are less than 1 cm thick each, and laminations that make it break quickly
along the parallel layers (fissile). The roof material of seam 10 on the west side is where this
specimen was collected. It was surrounded by sandstone that ranged from white to grey.
Figure 4.1 illustrates the dominance of clay minerals in this specimen (B,C). The second most
common material found in cracks is quartz (Fig. 4.1 B). Fine kaolinite granules dominate this
specimen (Fig. 4.1B;C).

58. 47
Figure 4.1: A diagram showing a shale specimen (Shale F-R): (A) hand specimen of shale
collected from the roof of seam 10; (B) Photomicrograph of shale under plane polarised
light; (C) Photomicrograph of shale under cross polarised light.: F-R= Far right, Qtz =
Quartz, Cl= Clay, C= organic matter.
Gritstone
Gritstone is an arenaceous sedimentary rock with a coarse texture (Fig. 4.2A). The
sample is pale to gray in hue, but sulfur stains have turned it yellow. It is a densely
packed, matrix-supported specimen. Quartz minerals that are still present dominate
it. Samples were taken from the south side of the box cut that was hosted by
sandstone. The predominant mineral is quartz (Fig. 4.2B,C), and kaolinite clay is
present as a cementing agent (Fig.4.2B). Minor microcline feldspar concentrations
are present (Fig. 4.2C). Muscovite is occurring in minor concentrations, it is
surrounded by quartz grains (Fig. 4.2C).

59. 48
Figure 4.2: Hand specimen of gritstone (Ply A F-R) (A) collected from the roof of
seam 10 on the west portion of the box cut: (B) Photomicrograph of gritstone under
crossed polarised light, (C) Photomicrograph of gritstone under plane polarised light;
F-R= Far right; Mc= Microcline; Qtz= Quartz; Cl= Clay; Mu=Muscovite.
Sandstone
Sandstone (Fig. 4.3A), is a clastic, arenaceous sedimentary rock with visible quartz
grains. It is a white, medium to fine grained quartz rich sandstone. Sand particles are
well packed as grains are of varying sizes. Sulfur stains (Fig. 4.3A) are present on the
specimen. This specimen was collected from the top of seam 10 on the south portion
of the box cut. This specimen is dominated by quartz grains with siliceous cement
(quartz fine matrix) (Fig. 4.3B). This quartz shows low relief and absent cleavage as
indicated by Tucker (1988). A lump of fine grains of kaolinite are enclosed by quartz
grains (Fig. 4.3B,C). This shows that kaolinite is occurring as a secondary mineral
due to weathering during the process of digenesis. A grain of muscovite with medium
relief and planar cleavage (Fig. 4.3C) is present with quartz grains. Since muscovite
is relatively weak, this implies abrasion of the source rock.

60. 49
Figure 4.3: A diagram showing a gritstone specimen (Ply A S-L) (A) collected from
the roof of seam 10 on the south portion of the box cut and Photomicrographs (B and
C) of the specimen under a petrographic microscope. Mc= Microcline, Qz= Quartz
and Cl= Clay.
Tucker (2001) indicated that the origin of quartz determines its size and shape. Quartz
grains in both samples are sub-angular to sub-rounded, this implies that grains were
transported from a distal crystalline source rock. Quartz grains from pre-existing
sedimentary rocks tend to be more rounded while those from the original crystalline
rocks are characterized by angular shapes (Tucker, 2001).
4.1.2 Description of Coal Samples
The Waterberg coalfield is characterized by coal consisting of alternating bands of
bright and dull coal (Fig. 4.4A;B). On the west portion of seam 10, layers of both
bright and dull coal were found to be thin as compared to those on the southern
portion. The coal specimen was mostly bright with prominent stains of sulphur and
calcite stains on the face of the box cut. Physically, the coal is characterized by high
density and it breaks evenly.

61. 50
Figure 4.4: Hand specimen showing alternating bands of bright and dull coal: (A)
alternating bands of dull and bright coal, (B) thin bands of bright and dull coal.
4.1.2.1 Maceral Point Count
A total of six representative samples were examined under a 100 mµ organic
petrology microscope. This was done to look into the organic and inorganic
components of the coal. The primary coal macerals and mineral matter in terms of
volume percent with and without mineral matter (inc. mm and mmf) were identified
(Table 4.1).
Maceral group analysis indicated that the Sekoko coal is inertinite-rich with the
content ranging from 28.3 to 90.3 vol% (Table 4.1) and having the average of 61.01
vol%. Vitrinite on the other hand has the content ranging from 8.0 to 70.5 vol% and
the average of 37.0 vol% on mineral matter free basis (mmf). Liptinite maceral
content was the least (Fig 4.1), it ranged from 1.2 to 2.8 vol% and was averaging
2.05 vol%. Therefore, the highest content of inertinite was found on seam 10 plyF S-
L which had 90.3 vol% of inertinite (Table 4.1) and (Fig 4.7).
These findings concur with Mokwena's (2012) results, which suggested that
Waterberg coal contains a higher amount of liptinite maceral compared to coal from
other coalfields, as well as varying amounts of vitrinite and liptinite.
The abundance of inertinite maceral in the study area proves that the Sekoko coal
mine is mining the lower portion the Grootegeluk formation which is rich in inertinite
macerals (Faure, 19933). Due to its oxidized and fragmented state, inertinite can be

62. 51
transported greater distances without changing compared to other macerals. As a
result, it can stay suspended in deeper and less turbulent environments. This is
supported by Beukes (1985) and Siepker (1986) who observed that lower portions of
coal formations have a greater proportion of inertinite while upper parts are rich in
vitrinite, which is consistent with the overall peat deposition..
Figure 4.5: Major maceral groups in coal.
Major Maceral groups in coal
100
80
60
40
20
seam 10 ply
C F-R
seam 11
comp
stockpile
seam 10 ply seam 10 ply seam 10 seam 10 ply
C S-L H S-L composite F S-L
Sample ID
Vitrinite Inertinite Liptinite Total reactive macerals
Concentration
(vol%)

63. 52
Table 4.1: Maceral group data analysis
Sample identification
seam 10 ply C
F-R
seam 11 comp
stockpile
seam 10 ply C S-L seam 10 ply H
S-L
seam 10
composite
seam 10 ply F S-
L
inc. mm Mmf inc. mm Mmf inc. mm Mmf inc. mm Mmf inc. mm Mmf inc. mm Mmf
Maceral
group
(vol%)
Vitrinite 40.1 44.6 20.4 22.8 43.2 48.4 58.6 70.5 25.2 27.3 6.4 8.0
Inertinite 47.5 52.8 67.0 75.0 44.4 49.8 23.6 28.3 64.2 69.9 72.2 90.3
Liptinite 2.4 2.6 2.0 2.2 1.6 1.8 1.0 1.2 2.6 2.8 1.4 1.7
Mineral
matter
10.0 10.6 10.8 16.8 8.0 20.0
Total reactive
macerals
48.3 53.6 28.8 32.2 49.2 55.1 61.8 74.3 31.2 33.8 10.8 13.4

64. 53
Figure 4.6: Micrographs showing identified Vitrinite (VIT), Inertinite (INT) macerals,
taken under white reflected light using an oil immersion lens for Seam 10 Ply C F-R.
VIT
INT VIT
INT
VIT
INT

65. 54
Figure 4.7: Micrographs showing identified Vitrinite (VIT), Liptinite (LIP) macerals,
taken under white reflected light using an oil immersion lens for Seam 11 Composite
sample.
INT
VIT VIT
VIT
VIT LIP
INT

66. 55
Figure 4.8: Micrographs showing identified Vitrinite (VIT), Inertinite (INT) and Liptinite
(LIP) macerals, taken under white reflected light using an oil immersion lens for
Seam 10 Ply C S-L.
INT
VIT INT VIT
VIT INT LIP
INT

67. 56
Figure 4.9: Micrographs showing identified Vitrinite (VIT), Inertinite (INT), Liptinite
(LIP) macerals, grain of Pyrite (P) and fractures, taken under white reflected light
using an oil immersion lens for Seam 10 Ply H S-L.
VIT INT VIT
Fracture
VIT P
INT LIP

68. 57
Fracture VIT Qz
INT Clay(Kaolinite)
Figure 4.10: Micrographs showing identified Vitrinite (VIT) macerals, taken under
white reflected light using an oil immersion lens for Seam 10 Composite.
Figure 4.11: Micrographs showing identified Vitrinite (VIT), Inertinite (INT) macerals,
Kaolinite clay and Quartz grains (Qz), taken under white reflected light using an oil
immersion lens for Seam 10 Ply F S-L.
VIT VIT

69. 58
4.1.2.2 Vitrinite Reflectance
Reflectance of Vitrinite results are shown in Table 4.2. Seam 10 PlyC F-R showed
the average random vitrinite reflectance of 0.617. Seam 11 composite and seam 10
plyC S-L are averaging 0.611 and 0.593 respectively. Seam 10 plyH S-L has an
average of 0.073 and seam 10 composite and seam 10 plyF S-L are averaging
0.062 and 0.752 respectively. Therefore, coal from Sekoko coal mine was ranked
according to UN-ECE (1998) to be medium bituminous rank C with the overall range
of 0.6 to 1 RoVmr (Table 4.3).
Table 4.2: Vitrinite reflectance data analysis
Sample identification: seam
10 ply
C F-R
seam 11
composit
e
stockpile
seam
10 ply
C S-L
seam
10 ply
H S-L
seam 10
composit
e
seam
10 ply
F S-L
Vitrinite Random 0.617 0.611% 0.593 0.073 0.062% 0.752
reflectanc vitrinite % % % %
e reflectance
standard 0.043 0.062% 0.058 0.606 0.061% 0.077
deviation % % % %
Measureme 106 102 97 100 100 77
nt count

70. 59
Table 4.3: Coal rank classification using vitrinite reflectance (%RoVmr) (After
Wanger et al., (2018))
Coal rank Low-rank Medium-rank High-rank
Lignite
Sub-
bituminous
Bituminous Semi-
anthracite
Anthracite Meta-
anthracite
Low Medium High
A/B C/D B A C B A
Vitrinite
reflectance
0.5 1.0 1.4 2.0 3.0 4.0 5.0
4.3 Mineralogical Characterisation of Host rocks and Coal
XRD analysis done on different plies of coal and the host rocks showed the presence
of different minerals, namely Quartz, Kaolinite, Pyrite, Muscovite, Microcline,
Anatase, Magnetite and Amorphous. The overburden or rocks overlying coal deposit
are highly concentrated with quartz and kaolinite as major minerals. Minor minerals
include muscovite, microcline and anatase.
Mineralogy of clastic sedimentary rocks
Faure (1993) stated that kaolinite, quartz, and trace amounts of anatase make up the
majority of the Grootegeluk Formation's lower component, while quartz, kaolinite,
montmorillonite-illite, and microcline are present in trace amounts in the formation's
upper parts.
Sandstone (Ply A. F-R) and gritstone (Ply A S-L) are high in quartz content than
shale (shale F-R) and similarly, shale is higher in kaolinite content that these
sedimentary rocks. Materials overlying the coal deposit are highly concentrated with
quartz with sandstone (Ply A. F-R) and gritstone (Ply A S-L) having the highest