The document discusses various mineral raw materials used in the ceramic industry in India. The principal materials are silica in the form of quartz and other minerals, and alumino-silicates like feldspars and clays. Major sources of silica are quartzite, sandstone and high silica sands. Important feldspar sources are pegmatites in Rajasthan, Bihar and Andhra Pradesh. Ball clays are found in Rajasthan and Gujarat while china clay deposits exist across India. Refractory materials include fireclay, quartz, dolomite, magnesite, serpentine, olivine and chromite. The document also provides details on the

1. PRAMODA G 1
Minerals for the Ceramic Industry
The Principal mineral raw materials for the manufacture of ceramic products are the silica in different forms
and the alumino-silicates. These minerals, in appropriate combinations, are fused at high temperatures to obtain
the required product. While silica minerals include quartz and other forms like silica sand, the alumino-silicates
comprise of the feldspars (orthoclase, microcline and albite) and clays. In addition, limestone and also minor
amounts of a large number of other minerals find use to certain extent in ceramics.
Silica:
For ceramic products, the quartz should be of good quality. Iron staining and iron oxide minerals are
considered as objectionable. The important geological sources for silica suitable for the ceramic industry are
the pegmatites (with well developed crystals of quartz), vein quartz, sandstones of high siliceous nature, high
silica sands and orthoquartzites.
In India, the major producing centres of silica are in the Sankargarh, Lohargarh and Bargarh regions (Uttar
Pradesh), Bundi and Dausa in Jaipur and Adalpur in Sawai Madhopur (Rajasthan), Shimoga district
(Karnataka), Burdwan district (West Bengal), Singbhum and Dhanbad districts (Bihar) and Guntur district
(Andhra Pradesh). Extensive deposits of quartzite suitable for glass manufacture occur in Mayurbhunj district
of Orissa. Some of the sandstones from Himmatnagar, Padharanali and Sankhera in Gujarat are suitable for the
ceramic industry.
Beneficiation: The common impurities are clay, slime, iron stains and iron silicate minerals such as
garnets. Feldspar and mica are objection苔ble. The raw material is ground in conventional manner and
deslimed to remove the clayey fraction. If iron is present as surface coating, this can be removed either by
scrubbing or by chemical treatment (like heating in a dilute solution of titanous sulphate with some hydrofluoric
acid). Tabling can be adopted for the removal of clayey minerals and the heavy minerals like ilmenite and
rutile.
The associated impurities such as mica and iron minerals can be removed by adopting flotation techniques. The
process is carried out in acid circuits (with pH between 2 and 3). Mica is floated by using a combination of fuel
of oil and some amine acetate. Then the pulp is treated with one of the petroleum sulphonates and iron is
removed in the subsequent stage of operation. In the final stage, feldspar is floated by using hydrofluoric acid
and amine acetate.
Feldspars:
Feldspars are used as fluxing material in the preparation of ceramic bodies, enamels and glazes. Commonly
potash feldspars (orthoclase and microcline) are used for this purpose and soda feldspar is chiefly used for
glazing purposes. Feldspars for use in ceramic industry should contain a minimum of 65-72% SiO2 and not less
than 4% Na2O.
Feldspar is one of the dominant ingredients in acid igneous rocks, particularly of granitic and pegmatitic
nature. Pegmatites are often zoned into distinct bands of quartz and feldspar. In India, the pegmatites of the
famous mica belts in Rajasthan, Bihar and Andhra Pradesh are the major sources of ceramic grade
feldspars. Rajasthan alone is responsible for about 90% of the total production coming from Bhilwara, Ajmer
and Alwar. The other producing areas are in Dhanbad, Santhal Pargana (Bihar), Chhindwara, Jabalpur, Shahdol
(Madhya Pradesh), Tiruchirapally Madurai, Salem, Coimbatore (Tamil Nadu), Burdwan and Purulia (West
Bengal) and Hassan (Karnataka). Indian feldspars are exported to the U.K., France, W. Germany, Italy and
Japan.
Beneficiation: The common impurities to be eliminated are the iron-bearing minerals such as garnet and
mica. The quarried material is broken and feldspar is removed easily by handpicking. The picked feldspar is
reduced in size by crushing in conventional crushers and by subsequent grinding in pulverizers. For glazing
purposes and for the manufacture of ceramic ware, iron contamination during size reduc負ion is avoided by

2. PRAMODA G 2
carrying out the grinding in pebble mills using flint pebbles as the grinding media. The flotation techniques,
similar to silica beneficiation, are also adopted for feldspar concentration.
Clays:
Clays have been classified on the basis of their physical properties and the industrial usage. Of the various
clays, ball and china clay are extensively used in ceramic industry. China clay and ball clay belong to the
kaolin group. Although the primary constituent is kaolinite in both these clays, ball clay has greater plasticity
and lesser refractoriness owing to the presence of mont衫orillonite in considerable amounts. It is normally
added to china clay to achieve greater strength and the required plasticity. These clays are a product of
weathering processes of feldspathic rocks. During weathering, the silica and iron oxides are partially leached
with the residue (essentially of an aluminium silicate in composition) forming the in-situ deposits. Depending
upon the efficiency of the weathering process, impurities like grit (siliceous particles) and iron oxide minerals
exist in different percent苔ges invarious clay deposits.
Ball Clay: Ball Clays with high plasticity ranges have been reported from Khajwana, Indawar, jodhpur and
Sheo areas in Rajasthan, Rampurda, Vagedia, Bagagela and Thoangadh areas in Gujarat, Kundra in Kerala,
parts of Chingleput district in Tamil Nadu and Dwarka-Tirumala in Andhra Pradesh.
China clay: Usage of china clay for ceramic industry depends on factors such as plasticity, shrinkage (after
drying and on firing), colour on firing and refractori要ess. The grit content should normally be less than 1%
and should never exceed 2%.
India has extensive deposits of china clays distributed in almost all the states. However, good deposits are in
Bhagalpur, Ranchi, Singbhum and Monghyr districts in Bihar; Mayurbhunj district in Orissa; Bankura and
Birbhum districts in West Bengal; Banda district in Uttar Pradesh; Barmer, Pali, Bikaner and Ajmer districts in
Rajasthan; Chingleput, North and South Arcot and Salem districts in Tamil Nadu; Adilabad, Anantapur, Nellore
and Guntur districts of Andhra Pradesh; Chanda and Ratnagiri districts in Maharashtra; Shimoga and Hassan
districts in Karnataka; Sabar虺antha district in Gujarat and Udhampur in Jammu and Kashmir.
Beneficiation: Major impurities in china clay are quartz, mica, felaspar and iron oxide minerals. Methods such
as sieving, washing, elutriation and levigation may be employed. Normally the washing is done by 'levigation'
process, which involves passing the clay slurry through a series of troughs or channels with different
slopes. This process aids in the settling of grit and other heavy mineral and floating of light fractions like
mica. Settling of finest quality clay takes place in the final tank. Decolourising of the clay is also attempted for
certain clays, which are coloured due to the presence of iron and titanium oxides. However, no elaborate
beneficiation techniques are employed in India and even the raw material that is marketed is not properly
graded and specified. This has been creating special problems to industries, particularly to those of smaller
sizes.
Minerals used in Refractories and Fillers
Refractories:
Materials that retain their shape and chemical identity without marked expansion at high temperatures are
required for lining kilns and furnaces and for many purposes in the electrical and chemical industries. These are
classed as refractories and technical ceramics which require a range of specialized properties and are derived
from both natural and synthetic sources. As used in the metallurgical industry, refractories should be capable of
withstanding a temperature of more than 1500o C without showing any signs of fusion. They should be strong
enough to bear the weight of molten metal, should not wear and tear easily, and must not react with the
melt. The more important natural materials used for the manufacture of refractories are listed in the table
below.
Raw Material Source Product and Use
Fireclay Fireclays are of sedimentary origin Refractory bricks for

3. PRAMODA G 3
and occur as horizons below the
coal seams
domestic fireplaces,
furnaces
Quartz sandstone,
quartzite
Pegmatites, sands and quartzites Silica bricks for furnaces
Kyanite and
sillimanite
Metamorphic rocks refractory bricks for high
temperature furnaces
Dolomite rock
Basic refractories stable in
the presence of slags, for
iron and steel furnaces.
Magnesite
Serpentine, olivine
rock & Chromite
Mullite Sparking plugs, other
electrical equipment
Alumina Kyanite and Sillimanite Technical ceramics
Talc, steatite Insulators in radio industry
Graphite Crucibles used for steel
manufacture
Barite
Fillers:
Fillers are minerals and materials used to add bulk or weight to paper, rubber, paints and other synthetic
products. They are derived mainly from inert clay minerals and from barite (BaSO4). They are also used as a
component of oilfield drilling muds. Barite is a common gangue mineral in hydrothermal and exhalative sulfide
deposits and it occasionally forms larger concentrations.
Availability of Material in India
Fire-clay:
Fireclays are of sedimentary origin and occur as horizons below the coal seams. In India fire clays from
Raniganj and Jharia coalfields are very important. The fireclays from Raniganj are excellent in quality. The
super-refractories are manufactured by blending them with certain proportions of bauxite from Lohardaga. In
general, the fireclays from both these coal fields occur within Barakars. Important deposits are around
Kumardhubi, Mugma, Garphalbari-胖ahibari region, Damagpria, Radhabhallabhpur, Pohargora Garb Dhamo,
Churulia and Pathardi. The Rajhara and Daltonganj coalfields are also important suppliers of plastic
fireclay. In Orissa, workable deposits of fireclay occur in Sambalpur, Cuttack, Sunde garh, Puri and Dhenkanal
districts. Fireclays from Belpahar are extensively used in steel plants.
In Madhya Pradesh, highly plastic and refractory clays are reported injabalpur, Betul, Bilaspur, Drug,
Hoshangabad and Satna districts. In Karnataka, good occurrences are reported in Shimoga, Bangalore and
Kolar districts. Good refractory fireclays also occur in Nizamabad, Asifabad, East Godavari and Cuddapah
districts (Andhra Pradesh) and North and South Arcot districts (Tamil Nadu). In Rajasthan, the fireclays are
distributed in jaisalmer, Sawai Madhopur and Bikaner areas.
Quartz, Sandstone & Quartzite:
The main sources of silica are the sands and quartzites. Important occurrences in India are as follows:
Bihar: Between Rakha Mines and Kendadih (Singbhum district), Rajagoan Hills (Gaya district), Ratanpur
(Monghyr district) and Bihar Shariff (Patna district).

4. PRAMODA G 4
Orissa: Khajuria-Pravasoni (Bamra district), jhargati and Garpati (Sambalpur district).
Karnataka: Dodguni area (Tumkur district).
Sands from Jabalpur (Madhya Pradesh) are also often used as refractory lining for the furnaces.
In recent years good sands have been obtained from the crushing of pure quartzose Vindhyan sandstones at
several localities in Uttar Pradesh, from Gondwana (Damuda) sandstone of the Raj Mahal hills, and from
Cretaceous sandstones and Archaean and other pure quartzites of some parts of Tamil Nadu and
Maharashtra. For silica brick manufacture, the raw material should contain at least 96 to 98% SiO2. While
magnesia and alkalies are objectionable, iron oxide in limited quantities helps in acting as a binder. Firing is
done around 1,480o
C in periodic kilns with 2% lime as binding material. The silica bricks have spalling with
temperature fluctuaions but strength is retained below the temperature of their fusion because of high thermal
conductivity.
Kyanite and Sillimanite:
Kyanite and sillimanite are similar in chemical composition (Al2O3.SiO2) but differ in crystal structure. They
occur in metamorphic aluminous rocks. The main occurrence of kyanite in India is in Lapsa Buru in Bihar,
where it occurs with quartz along a 100 km long zone. Large deposits are also mined in Bhandara district of
Maharashtra. The most important occurrences of sillimanite are in the Khasi Hills of Assam and in Meghalaya
and Rewa in Madhya Pradesh.
Dolomite:
For refractory usage, dolomite should have an equimolecular proportion of CaCO3, and MgCO3. It must be low
in SiO2, Fe2O3 and Al2O3 (together less than 3%). For calcined dolomite, the specifications are very rigid and
SiO2 and Al2O3 should not exceed 1% each. Calcined dolomite is distinctly preferred over the raw dolomite for
maintaining the open-hearth steel furnaces. Dolomite and dolomitic limestone are used extensively for the steel
furnaces owing to the low cost and easy availability in contrast to magnesite.
Workable deposits of dolomite used in refractories are reported in Orissa around Birmitrapur and Purnapani
areas of Sundergarh district. These are generally high in silica and are used in furnace operations at TISCO,
Rourkela and Durgapur. The dolomite occurs in a band of 300 metres width over a length of 7,000 metres and
depth up to 50 metres. The estimated reserves are 252 million tonnes.
In Madhya Pradesh, the marbles of Narmadaghat (Jabalpur district) are dolomitic. Dolomite from Bilaspur and
Satna districts is used in open-hearth furnaces of Rourkela and Bhilai steel plants. In Karnataka, refractory
grade dolomite is worked around Sankar茆udda in Shimoga district and is the principal source of refractories
for use in the steel plant at Bhadravati.
The total reserves of blast furnace and steel melting shop grades of dolomite in India are estimated at 720 and
428 million tonnes respectively.
The dolomite bricks are made on conversion to di-calcium or tri-calcium silicates. In the case of di-calcium
silicate, the dusting encountered during cooling can be avoided by adding minor amounts of Fe2O3 within
limits. The tri-calcium silicate is obtained by adding 15% serpentine to powdered dolomite and calcining the
mixture at 1,600o
C in a rotary kiln.
Magnesite:
Large deposits of magnesite (MgCO3) occur in the district of Salem as veins associated with other magnesian
rocks such as dolomite, serpentines, etc. The magnesite is believed to be an alteration-product of the dunites
(peridotite) and other basic magnesian rocks of Salem. When freshly broken it is of a dazzling white colour and
hence the magnesite-veins traversing the country have been named the Chalk hills of Salem. The magnesite of
Salem is of a high degree of purity (MgO 46.4 %), is easily obtained and, when calcined at a high temperature,
yields a material of great refractoriness. Other places in India also contain magnesite-veins traversing basic
rocks, viz. Coorg, Coimbatore, Mysore, Almora and parts of Eastern Himalayas.

5. PRAMODA G 5
Serpentine, Olivine Rock and Chromite:
Dunites (rocks rich in olivine) occur as a product of magmatic differentiation in the form of layered masses and
veins associated with ultra-basic, intrusive rocks, like chromites, peridotites, serpentines, etc. Serpentinites
(rocks rich in serpentine) occur as products of weathering and alteration of olivine rich rocks. These occur in
Karnataka, in several districts of Orissa (chiefly Keonj苑ar), and in Singhbhum. The Orissa reserves are the
largest computed at over 3.5 million tons. Less important deposits have been found in parts of Tamil Nadu and
in Ratnagiri in Maharashtra. Some chromite occurs in the " Chalk hills " (magnesite-veins) near Salem, but it is
not worked. Large deposits of chromite occurring in dunite intrusions forming mountain-masses have been dis
苞overed in the Cretaceous volcanics of Burzil and Dras valley of Ladakh, Kashmir.
Kyanite and Sillimanite:
Kyanite and sillimanite are similar in chemical composition (Al2O3) . However, they differ in their crystal
structure and
physical behaviour. They occur in metamorphic altiminous rocks. India has the richest deposits of kyanite and
sillimanite in the world.
Talc and Steatite:
Talc and steatite occur widely in India, forming large masses in the Archaean and Dharwar rocks of the
Peninsula. Workable deposits occur in Bihar, Jabalpur, Salem, Idar and Jaipur. The Rajasthan, the deposits
occur as thick lenticular beds of wide extent in the schists. Some of these beds persist for miles. At most of
these places steatite is quarried in considerable quantities for commercial purposes. In its geological relations,
steatite is often associated with dolomite (as in Jabalpur) and other magnesian rocks, and it is probable that it is
derived from these rocks by metamorphic processes resulting in the con赳ersion of the magnesium carbonate
into the hydrated silicate. In other cases it is the final product of the alteration of ultra-basic and basic eruptive
rocks.
Graphite:
Graphite deposits in India are associated with metamorphic rocks (schists and gneisses) and limestone. Graphite
graphite is being mined in Latehar and palamau districts of Jharkhand; Bargarh, Nuapada, Rayagarh and
Bolangir districts in Orissa and madurai and Sivaganga districts of Tamil Nadu. Graphite mines are mostly
small, except for a few underground mines in Orissa, which are faced with the problem of water seepage.
Besides the above mentioned mines, graphite also occurs in Sambalpur, Dhenkanal, Koraput, Phulbani and
Kalahandi districts of Orissa;
Graphite crucibles used for steel are approximately of 50% graphite, 30% bond clay, 10% sand and 10% kaolin
while those used for brass have 45% graphite, 35% bond clay, 10% grog and 10% kaolin. The graphite for
crucibles should contain 80% fixed carbon. Mica, carbonates and sulphur (in the form of pyrite) are the
undesirable impurities. While mica fuses causing holes in the crucibles, carbonates and pryite dissociate
resulting in volume changes. Graphite is also used as a foundry facing material.
Barite:
Barite is used as a pig衫ent for mixing with white lead, as a flux in the smelting of iron and manganese, in
paper-manufacture as a filler, and in pottery-glazes, etc. The whiter and better-quality barite is used in the local
manufacture of paints (lithophone); the coloured variety is used in making heavy drilling mud by the oil
companies.
Barite occurs in sufficient quantities at many places in India in the form of veins and as beds in shales. The
chief localities for barite mining are Cuddapah, Kurnool, Khammam and Prakasum districts of Andhra Pradesh;
Sirmur district Himachal Pradesh; and Udaipur district of Rajasthan. Besides these, barite also occurs in the
Kurnool district of Andhra Pradesh; Alwar in Rajasthan; Salem in Tamil Nadu; and Sleemanabad (in the
Jabalpur district). Barite mines in India are worked by opencast method.

6. PRAMODA G 6
Minerals used in the Fertilizer Industry
During the last four decades, with the emphasis on agricultural produc負ion in India, increased attention was
given to the manufacture of chemical fertilizers. The fertilizer plants use the raw materials both from natural
sources and from the chemical materials. Gypsum, pyrite and rock phosphates form the principal mineral
sources. While the first two find extensive use in the manufacture of sulfate fertilizers, the rock phosphates are
mainly utilized in the production of phosphate fertilizer.
Source of various constituents in Fertilizers
Principal nutrient Source
Nitrogen (N)
organic fertilizers including animal manure, plant waste,
seaweed, fishmeal, dried blood etc, give exchangable nitrogen
nitrogen fixing bacteria in soil or in symbiotic relationship
with legumes
nitrates, non-marine evaporates of Chile
ammonia and its derivatives from petrochemical plants
Potash (K)
organic fertilisers, especially manure
bittern salts of marine evaporites
Lime (Ca)
shells and bone
carbonate rocks including limestone, tufa, calcrete
Phosphates (P)
bone meal, manure
guano (consolidated droppings of sea birds, from oceanic
islands, now largely worked out)
superphosphate derived from phosphorite
basic slag byproduct of steel production
Sulfur (S)
salt domes (reduction of gypsum)
iron sulphides
GYPSUM DEPOSITS
Gypsum is a hydrated calcium sulfate (CaSO4.2H20 ) and its an虐ydrous form (CaSO4) is known as
anhydrite. Deposits of gypsum are either of sedimentary origin (bedded type) or of marine evaporate
nature. Gypsum finds extensive use in the cement, paper, textile and paint industries. The mineral, calcined
around 200o
C loses 75% of its water and the product, known by its trade name as 'plaster of paris', is widely
used in building industry as a good finishing material. It can be moulded into any shape with the addition of
water and sets to a hard mass.
In India, gypsum is produced in Rajasthan. Tamil Nadu, Uttar Pradesh, Gujarat and Maharashtra. Of these, the
first three are the important producers with Rajasthan possessing around 95% of the total Indian reserves
(estimated to be around 1,000 m tonnes). The deposits in Rajasthan are situated mainly in Bikaner, jodhpur,
Nagaur and jaisalmer districts. The Rajasthan occurrences are associated with the Vindhyan limestones.

7. PRAMODA G 7
In Tamil Nadu the deposits are situated in Tiruchirapalli, Coimbatore and Ramanathapuram districts and are
associated with the shales in Cretaceous sequence. The gypsum from these sources is chiefly utilized in the
cement and pottery industry. In Uttar Pradesh, deposits are reported in Dehradun, Garhwal and Nanital
districts. The Majhara deposit in Dehradun district and Lakshmanjhula in Garhwal district are exploited at
present.
For use in fertilizer industry, gypsum with a minimum of 87% CaSO4.2H2O is preferred. The Sindri fertilizer
plant gets its main supply from the Bikaner deposits.
PYRITE DEPOSITS
Sulfur and pyrite (FeS2) are the principal raw materials in the manufacture of sulfuric acid which forms the
back-bone of many modern industries such as fertilizers, chemicals, paints and textiles. Pyrite is either mined as
a principal mineral or is recovered from the sulfide assemblages of copper, lead-zinc, gold and other metallic
ore deposits.
In India, pyrite deposits occur in Bihar, Karnataka, Rajasthan and Tamil Nadu. However, the largest deposits
are from Amjhore region in Shahabad district of Bihar where pyrite occurs as a uniform bed of about one metre
thickness in the Bijaigarh black shales of Kaimur series (Vindhyan system). The deposit (located at nine places
within the Amjhore region) has a remarkable conformity with the overlying and underlying Vindhyan
formations and is confined to a single stratigraphic horizon. Two types of pyrite occurrences have been
reported: the massive cryptocrystalline variety, which forms the bulk of the deposit and the fine pyrite grains,
disseminated within the black shale. About 390 million tonnes of pyrite (with 48% S) are estimated to be
available within an area of 120 sq. km in Amjhore region.
In Karnataka, pyrite deposits occur around Ingaldahl in Chitalrug district. The mineralization is localized in the
ferruginous chert bands interbanded with Dharwarian greenstones in the eastern flank of an anticlinal
structure. It may be noted that copper mineralization in this region is on the western flank of this structure. The
Ingaldahl pyrite reserves are estimated to be around 2.0 million. tonnes (of 20-30% S). The deposits in
Rajasthan occur at Saladipura and the inferred reserves are of the order of85 million tonnes (with 22% S). In
Tamil Nadu, the deposits are located around Polur in the Thaniyar reserve forest.
Besides the above occurrences, pyrite is also associated with gold, copper, lead and zinc deposits as also in
Tertiary coals. In the metallic ores, after the recovery of primary minerals the tailings containing pyrite are
discarded in India. Plans are underway to recover and utilize pyrite from such tailings, Sizeable deposits of
sulphur have been reported from Puga valley in Ladakh.
In India, the requirements of sulphur are of the order of 3,00,000 tonnes per year. At present the mining activity
is at Amjhore by the state-owned Pyrites, Phophates and Chemicals Ltd. A sulphuric acid plant of 400 tonnes
per day capacity has been set up at Sindri in Bihar.
ROCK PHOSPHATE DEPOSTS
Phosphate deposits of sedimentary origin and of economic importance are known as phosphorites or rock
phosphates. The formation of these is restricted to marine environments and is a result of deposition under
specific pH conditions from the phosphorus-bearing solutions derived from the weathering of phosphate
minerals like apatite of igneous source. It is thought that redox potential does not play any role in their
formation. In all the phosphate minerals, phosphorus exists in its highest valent state,

8. PRAMODA G 8
In India, with the development of superphosphate fertilizer in苓ustry, the exploration for rock phosphate
deposits has been accelerated. Deposits of economic significance are reported from Rajasthan and Uttar
Pradesh. In Rajasthan, they are located in Udaipur and jaisalmer districts. The Udaipur deposits occur around
Jhamar Kotra area, Kanpur region (Kanpur, Karbaria Ka Gurha and Maton blocks) and Dakan Kotra area. The
phosphorites are confined to limestone or cherty quartzite and are in the form of lenticular masses of variable
thickness with the P2O5 content between 15 and 25%. However, the published analyses for Maton deposits
indicate P2O5 as high as 36%. The Jaisalmer deposits are mainly located in the Fatehgarh area where the
phosphorite horizon was associated with the Mesozoic sandstones. The P2O5 content varies from 5 to
15%. Two types of mineral associations are reported from Rajasthan deposits: pellets of collaphane and black
chert in calcare觔us shaly sandstones and the banded phosphorites (of alternate collophane with quartz on
calcite bands) with limestone bands. The basic characteristic feature of these phosphorites is their association
with limestones, which distinguishes the same from those of Uttar Pradesh. Around 80 million tonnes are
estimated to be available in Rajasthan.
In Uttar Pradesh, the deposits occur mainly at Mussoorie and Meldeota, although in all about 10 deposits are
located. The phos計hate-bearing zones, thickness varying from a few centimetres to about 15 metres at places,
are mainly restricted to chert and carbonaceous shale formations of Lower Tals or at the contact of the
underlying argillaceous limestones of Upper Krols. Three varieties of phosphorite -- granular, pelletal and
nodular -- have been reported. The P2O5content of these deposits varies between 15 and 35%. The deposits
from Uttar Pradesh contain the collophane species of phosphates together with quartz, calcite, chert, muscovite
and clay minerals. The development of the Mussoorie deposits is beset with several difficulties such as their
complex mineralogy, lack of precise estimates as regards the quantity and quality of ore available, remoteness
of the deposits and the need for underground mining.
In India, the major share of the requirements for rock phosphates is met from the imports of the order of
5,75,000 tonnes per year while the production is around 6,44,000 tonnes. A beneficiation plant is being set up
at Matas near Udaipur by Hindustan Zinc Limited to upgrade the phosphorite from 25% P2O5 to >32%
P2O5 with consequent reduction of silica. It is planned to send these concentrates to the superphosphate unit at
Debari smelting plant.