This document discusses different types of rocks classified based on their formation processes and mineral/chemical composition. It summarizes key rock types as follows: 1) Igneous rocks such as granite, syenite, diorite, gabbro and dolerite are formed by cooling of magma and are divided into plutonic and volcanic types. 2) Sedimentary rocks like sandstone form at the Earth's surface through compaction/cementation of sediments and include varieties based on grain size and cementing material. 3) Metamorphic rocks form from existing rocks subjected to high temperature and pressure, altering their mineral composition from the original rock type. Rock types transform through the geological rock cycle

1. Rocks are classified by mineral and
chemical composition, by the texture
of the constituent particles and by the
processes that formed them. These
indicators separate rocks into igneous,
sedimentary and metamorphic. They
are further classified according to
particle size. The transformation of one
rock type to another is described by
the geological model called the rock
cycle

2. Igneous rocks are formed when molten magma cools and are divided
into two main categories: plutonic rock and volcanic. Plutonic or
intrusive rocks result when magma cools and crystallizes slowly within
the Earth's crust (example granite), while volcanic or extrusive rocks
result from magma reaching the surface either as lava or fragmental
ejecta (examples pumice and basalt

3. Sedimentary rocks are formed by deposition of
either clastic sediments, organic matter, or
chemical precipitates (evaporites), followed by
compaction of the particulate matter and
cementation during diagenesis. Sedimentary
rocks form at or near the Earth's surface. Mud
rocks comprise 65% (mudstone, shale and
siltstone); sandstones 20 to 25% and carbonate
rocks 10 to 15% (limestone and dolostone

4. Metamorphic rocks are formed by subjecting
any rock type (including previously formed
metamorphic rock) to different temperature
and pressure conditions than those in which
the original rock was formed. These
temperatures and pressures are always higher
than those at the Earth's surface and must be
sufficiently high so as to change the original
minerals into other mineral types or else into
other forms of the same minerals (e.g. by
recrystallisation).

6. GRANITE

7. GRANITE POLISHED

8. 1.GRANITE
•Plutonic rock body
•Holocrystalline and leucocratic
•Acidic and oversaturated – very rich in silica (72 %) - free quartz.
•ESSENTIAL MINERALS
•Quartz (25 – 40 %) and Feldspar (Both orthoclase and 50 % plagioclase
(albite or oligoclase ) or microcline.
•ACCESSORY MINERALS
•Mica (biotite / light mica muscovite) or both (Hornblende – soda rich
minerals, augite, tourmaline .
•Alkaline type – Reibeckite and Aegirite
•Apatite, Zircon, sphene, garnet, magnetite, pyrite, epidote
•High percentages for soda and potash (helps to form mica) – Feldspar.
•Low ferromagnesian content
•Titanium for sphene
•Phosphorous for apatite.

10. •TEXTURE
•Interlocking phaneric Coarse grained texture (medium to fine grained)
•Equigranular
•Porphyritic texture – Bigger surrounded by smaller crystals.
•Fine –grained variety – microgranite
•As a chilled margin to a larger mass or as a vein rock.
•Reibeckite bearing microgranite – CURLING STONES
•GRAPHIC TEXTURE – due to an inter-growth of quartz and feldspar in
which oriented angular pockets of quartz have crystallized within the
feldspar (orthoclase / microcline) in parallel positions – Hebrew writing.
•If developed on a fine – grained scale (micrographic) –
GRANOPHYRE.
GRAPHIC TEXTURE

11. •STRUCTURE
•Compact dense massive hard rock - mural joints – two sets vertical,
& (all mutually perpendicular) one set horizontal (Rectangular blocks)
•Facilitating the quarrying processes.
•Groups of adjacent quartz areas show simultaneous extinction
between crossed nicols, indicating that each group forms part of a
SINGLE CRYSTAL STRUCTURE which extends through the feldspar
– due simultaneous crystallization of the two minerals, which form a
mixture in the eutectic proportions – The Eutectic mixture of two solids
is the one which has the lowest freezing points.
•VARIETIES
•chief mineral present
•Muscovite granite
•mica granite)
•Hornblende granite,
•Tourmaline granite.

12. ENGINEERING PROPERTIES
•GRANITE – MASSIVE, unstratified and dense (specific gravity – 2.6 –2.8;
density –2500 to 2650 kg/cm2)
•Strong and competent ; compressive strength – 1000 – 2500 kg /cm3
•Interlocking texture – keeps minerals firmly held. Cohesion – contribute to
strength of the rock.
•Equigranular / porphyritic texture
•on polishing - mosaic appearance
•mottled appearance
•No porous (porosity - < 1 %); No permeable (absorption – 0.5 t0 1.2.%)
•No saturation / percolation of water
•No weathering processes.
•DURABLE
•Rich in silica - resistant to decay
•Hard minerals – tough – resistant to abrasion ( hardness coefficient = 18)
•Presence of mural joints - easy quarrying
•Pleasing colours
•Superb polishing
•Resistance to FIRE AND FOREST RESISTANCE

13. SYENITE

14. 2.SYENITE
•SYENITE – Named after Syene, Egypt)
•Plutonic representative – related rocks contain a higher proportion
of Alkalies.
•Syenite – large content of Alkali Feldspar. Sometimes by the
presence of feldspathoids.
•Porphyry – Dyke equivalent
•Trachyte – Extrusive equivalent.
•MINERAL COMPOSITION
•80 – 85 % Made up of feldspar.
•Rich in alkalies K-feldspar (Orthoclase) – Chief constituent 50 % of
the rocks with a smaller amount of plagioclase (Oligoclase)
ACCESSORY MINERALS
•Chief accessory Mafic minerals – Hornblende and Biotite, Pyroxene
•Iron oxides, Apatite, Sphene, zircon
•Feldspathoids – Under saturated syenites ; Nepheline syenite

15. Equigranular, Coarse grained texture,

16. TEXTURE
•Equigranular, Coarse grained, holocrystalline, sometimes porphyritic textures.
•Granitic – interlocking crystal plates.
•VARIETIES
•Hornblende syenite
•Augite syenite
•Biotite syenite, quartz syenite
•LAURVIKITE – Soda rich syenite (with average Na2O = 6 %)
•Porphyry = syenite – porphyry
•Porphyritic crystals – orthoclase in a microcrystalline base made of feldspar with
hornblende or biotite.
•RHOMPORPHYRY – Dyke = Laurvikite.
OCCURRENCES
•Marginal facies about granite intrusions
• / stocks / laccoliths.

17. DIORITE

18. 3. DIORITE
•Plutonic rocks
•Intermediate between acid and basic rocks
•Dark appearance
•ESSENTIAL MINERALS
•Feldspar - Plagioclase ( Normally Oligoclase - Andesine )
•Chief dark minerals Hornblende, Biotite present
•Pyroxene rare
•ACCESSORY MINERALS
•Apatite
•Sphene
•Iron oxide
•Biotite
•Quartz
•Little orthoclase
•15 – 40 % Mafic minerals
•TEXTURE
•Equigranular, Holocrystalline, coarse to medium
•Rarely Porphyritic texture
•VARIETIES
•Diorite – (= Andesine, feldspar + Hornblende) Augite – diorite, Biotite – diorite; quartz - diorite
•Mircrodiorite – fine grained varieties
OCCURRENCES
•Marginal facies of diorite, stocks and bosses.

19. GABBRO

20. 4. GABBRO
•ESSENTIAL MINERALS
•Plagioclase ( Labradorite to Anorthite)
•Monoclinic pyroxene, e.g. Augite / Diallage
•ACCESSORY MINERALS
•Illmenite
•Apatite
•Biotite
•Hornblende
•TEXTURE
•Coarse crystalline – rarely porphyritic
•Dark in colour ( grey to black / greenish black) high proportions of mafic minerals. –
grey tint – plagioclase.
•Interlocking crystal plates.
•DECOMPOSITION
•Serpentine after olivine
•Chlorite after pyroxene
•VARIETIES
•Norite - Gabbro with Enstatite / hypersthene instead of Augite.
•Troctolite – olivine – Gabbro without Augite.
•Quartz Gabbro – Little interstitial quartz liquor
•Essexite / Nepheline Gabbro – Feldspthoidal variety.

21. PEGMATITES

22. 5.PEGMATITES
•GENERAL
•Holocrystalline ; phaneric - Very coarse grained rocks
•Interlocking texture
•Acidic & oversaturated
•Resemble granites in mineralogy and granite pegmatite
•MINERAL COMPOSITION
•Resemble granites in mineralogy and granite pegmatite
•Granite pegmatites
•Alkali feldspar and quartz
•Rich in muscovite and biotite micas
•Rich in rare volatiles – tourmaline, beryl, topaz , apatite, fluorspar, lepidolite
•Store house of valuable and rare minerals.
•Syenite pegmatite
•Rare earth metals like zirconium, cerium, lanthanum, uranium, thorium
•TEXTURE
•Holocrystalline ; phaneric - Very coarse grained rocks
•Interlocking texture
•Occur as dykes and veins in the outer parts of an intrusive mass and in the
surrounding country rocks.
•Residual portion of the magma.
•Granite – pegmaties –quartz, microcline and mica.

23. DIAGNOSTIC CHARACTERS
•Very large sized minerals
•An extremely large sized Beryl crystal 18 feet long – weight 18 ton (albany, maine)
•Occurrence of uncommon minerals - Rich in volatile constituents – tourmaline &
Beryl.
•Late injections in the cooling history.
•Volatiles – aqueous act as fluxes and lower the crystallization temperature of
minerals. (lithium, Tungsten, cerium, thorium)
•MODE OF OCCURRENCE
•Products of solidification of final magmatic residues; rich in volatile constituents
•Mainly aqueous in character
•Plutonic mass margins - injected into the solidified and cracked margin of and into
the surrounding country rock.
•Pegmatite – veins, sheets, dykes
•Economic deposits - mica – muscovite – phlogopite.
PHYSICAL PROPERTIES
•Like granite – similar mineral content; interlocking texture
•Engineering point of view – larger crystals - not uniform throughout – presence of
mica with excellent cleavage – weak rock
•So unsuitable for building stone and foundation
•Economically important.

24. DOLERITE

25. 6.DOLERITE
•Dark, heavy, fine grained igneous rock; Melanocratic – dark colour
•Intermediate rocks. Dykes / sills – hypabyssal rock
•Saturated
•Dark greenish or black colour
•Gabbro - fine compared to coarse grained gabbro
•Basalt – coarser compared to fine grained basalt
•Dolerite is coarser than basalt, finer than gabbro
•ESSENTIAL MINERALS
•Plagioclase feldspar ( Labradorite to Anorthite)
•Monoclinic pyroxene, ( Augite)
•ACCESSORY MINERALS
•Illmenite
•Hypersthene
•Iron oxides
•Apatite
•Biotite
•Hornblende

26. •TEXTURE
•Equigranular
•OPHITIC TEXTURE – phaneric Fine – grained ; when the lath – shaped plagioclase
crystals are partly or completely enclosed in AUGITE
•Intergranular – occur as granules between the plagioclase laths.
•Interlocking of the chief mineral components gives a very strong, tough rock.
•Dolerite porphyry – white feldspar grain- phenocrysts
•STRUCTURE
•VERY DENSE, MASSIVE COMPACT – neither porous nor permeable
•Heavier than granite – richer in mafic minerals
OPHITIC TEXTURE

27. •DOLERITE VARIETIES
•Normal Dolerite - Labradorite + Augite + Iron oxide.
•Olivine Dolerite
•Hypersthene Dolerite
•Quartz Dolerite
•TESCHENITE - Analcite – Dolerite – Undersaturated type.
•Diabase – Much Altered Dolerites.
•Basic composition - High crushing strength – used as
road metal.
•MODE OF OCCURRENCE
•Intrusive rock as dyke less commonly sills in granite
•Linear ridges or trends

28. BASALT

30. •7.BASALT
•ESSENTIAL MINERALS
•Feldspar – Plagioclase
• ( Labradorite) – Only in few cases,
Andesine, Oligoclase, Albite.
•Monoclinic pyroxene, Augite
•Iron oxide
•ACCESSORY MINERALS
•Illmenite
•Magnetite

31. •TEXTURE
•Vesicular and amygdoloidal textures; Abundant gives cavities –
vesicular. Vesicle fillings – calcite, chlorite, zeolites, chalcedony
•Porphyritic texture – Olivine as a rule – Phenocrysts; Fine
grained to glassy, porphyritic texture.
•Phenocrysts --- More Calcite, plagioclase, bytownite / anorthite
•Groundmass – Labradorite feldspar (chief) Augite both
groundmass and phenocrysts.
•Dark gray to black in colour

32. •DECOMPOSITION
•Olivine show alteration to Serpentine.
•VARIETIES
•Tachylite – Basalt glass – chilled base to flows of basalt lava –
chilled margins of dykes.
•Olivine basalt (common varieties)
•Quartz basalt
•Nepheline basalt
•Leucite basalt
•SPLITES – PILLOW STRUCTURE - soda rich basalts –
plagioclase mainly Albite
•Amygadoloidal - weathered types – Melaphyre
•OCCURRENCE
•Volcanic rocks; form extensive lava flows – small dykes.

33. •ENGINEERING IMPORTANCE OF BASALT
•Serious problems in Foundation design,
especially for dams
•Soil horizon over flow – buried another
subsequent to flow
•Ground flow by inhibit groundwater flow.
•Columnar joints – hexagonal jointing.

34. Sandstone

35. 8.SANDSTONE
•NATURE
•Arenaceous
•Color depends upon cementing materials
•Silica / calcite – light in colour
•Iron oxide – red or reddish brown
•MINERAL COMPOSITION
•Essential mineral constituent - quartz
•Accessory minerals – feldspar / apatite mica, garnet, zircon, tourmaline, magnetite.
•Cementing material – silica, calcite, iron oxide, clay, chlorite
•TEXTURE
•Entirely well sorted, sub angular / rounded sand grains
•Coarse grained – 2 to 0.5 mm
•Medium grained – 0.5. to 0.25 mm
•Fine grained – 0.25 to 0.1 mm

36. •STRUCTURE
•Stratification
•Current
bedding
•Ripple marks
•Rain prints
•Current bedding
•Ripple marks
•Rain prints
•Stratification

37. •VARIETIES
•ORTHOQUARTZITE – siliceous sandstone
quartz cemented by silica.
•GRIT – sharply angular grains
•ARKOSE – notable amount of feldspar
•GRAYWACKE – grey colored rock poorly
sorted angular fragments of quartz / basic
igneous rocks.
•GLAUCONITIC SANDSTONE - glauconite
ARKOSE
GRAYWACKE
GLAUCONITIC SANDSTONE
•GRIT – sharply angular grains

38. •ENGINEERING IMPORTANCE
•Cementing materials –
•silica / iron – Hard rock of excellent quality - suitable for foundation.
•If clay / calcite – inferior quality – Not suitable for foundation.
•STRENGTH & PERMEABILITY – depends on the type and degree
of cementation.
•Sandstone with fractures, jointing and foldings - weaken the rock -
incompetent.
•Fine to coarse grained – fairly v competent bearing material – soft
materials – inter – spaced.
•ARGILLACEOUS SANDSTONE
•Clayey - air and water slaking -- production of a chemical change in
lime (Ca CO3) by mixing it with water and clay.
•GRANULAR NATURE – porous and permeable – water – bearing
formations. Highly desirable for developing groundwater aquifers.
•Trouble some – excavation.
• Good building materials

40. 9.LIMESTONE
•NATURE
•Calcareous Limestone
•CaCO3 (Calcite)
•CaMg (CO3)2
•Chemically formed
•Inorganically formed
•Organically formed
•CHEMICAL LIMESTONE
•CaCO3 90 %; 10 % MgCO3; 5 % SiO2
•Shallow water
•White when pure
•Various color due to impurities pink, gray, black – soft, massive / fine grained.
•STRUCTURE
•Stratification
•Current bedding
•Laminated
•Thinly bedded

41. •VARIETIES
CHALK – soft, white very fine grained – Globigerina
ooze.
STALACITE, STALAGMITE , DRIPSTONE
TRAVERTINE – hot spring
KANKAR – Nodular or concretionary form in CaCO3 -
evaporation of sub-soil water.
SHELL LIMESTONE
FLAGGY LIMESTONE – Splitting into thin slabs
ARGILLACEOUS LIMESTONE
SILICEOUS LIMESTONE
CORAL LIMESTONE
MARL
ALGAL LIMESTONE

42. TRAVERTINE – hot spring
CORAL LIMESTONE- organic

43. ALGAL LIMESTONE

44. ALGAL LIMESTONE

45. •ENGINEERING IMPORTANCE
•Massive and compact limestone
•Dolomite – competent foundation material – texture – fine and crystalline
•Foundation material – impermeable and loose textured (brecciated) and
porous
•Clay, silica / other impurities – strong, influence on their satisfactory use in
construction.
•Moderate resistance to abrasion and impact low hardness, equal to basalt.
•CHALK – variety of limestone – not regarded as competent bearing material
for heavy structures.
•Presence of shale – unsound
•Chert - bearing rock – material of high expansion / reactive with alkali in
Portland cement.
•Considerable leakage – cavernous formation under a dam / reservoir.

46. Conglomerate
Conglomerate rocks are sedimentary rocks.
They are made up of large sediments like sand
and pebbles. The sediment is so large that
pressure alone cannot hold the rock together;
it is also cemented together with dissolved
minerals.

47. 9.CONGLOMERATES
•Rudaceous group
•Rounded fragments of various sizes
•Cemented by clayey or ferruginous or mixed matrix.
•Roundness: transported considerable distance.

48. TYPES OF CONGLOMERATE
•Basal conglomerates
•Glacial conglomerates
•Volcanic conglomerates
•Oligomictic – simple in composition – quartz, chert, calcite
•Polymictic – grave of igneous sedimentary and metamorphic origins.
•Geologically – shallow water conditions
•Compositional heterogeneity or pebbles and cementing material – weakens
rocks
•Incomplete cementation – porosity and permeability (good aquifer) –
Incompetent rocks.
•Rounded grains – no grip of cements – less cohesion - undesirable at the
size of foundation.

49. SHALE

50. 10.SHALE
•NATURE
•ARGILLACEOUS
•Color variable
•Soft scratched by a knife.
•Fissility
•MINERAL COMPOSITION
•Made up of clay minerals Kaolinite, Montmorillinite, Illite. Quartz, mica, chlorite
•TEXTURE
•Very fine grained – Less than 0.01 mm.
•STRUCTURE
•Lamination
•Ripple marks
•Organic structures
•VARIETIES
•CALCAREOUS SHALE – Calcium carbonate.
•FERRUGINOUS SHALE – Iron oxide
•CARBONACEOUS SHALE – Organic matters
•SILTSTONE – compact silt (0.01 – 0.1 mm).
•MUDSTONE

51. •ENGINEERING IMPORTANCE
•Laminated sedimentary rocks
•Dark color - predominantly of clay – sized particles with small
percentages of sand / silt size particles.
•Degree of Induration varies
•Compaction shale – soften, slake and swell on exposure when
alternate wetting and drying revert to the original clayey.
•Expansive shale – crack foundation / pavements.
•Shale sliding along bedding planes – planes of weakness.
•Shales when saturated with water exerts pressure – lubricating
material – slips due to overburden – Foundation site - unsuitable
•Incompetent – plastically subsidence
•Fissility – unsuitable for construction material, road metal, railway
ballast, tunneling.

52. Breccia

53. 11.BRECCIA - < 2 mm
•Mechanically formed sedimentary rocks; Rudite – Rudaceous rocks
•Sharp, angular edges
•Angular fragments of heterogenous composition – embeded – Fine matrix of
clayey material.
•Little transportation from parent rocks.
TYPES OF BRECCIA
•Basal breccias :- overland areas.
•Fault breccias
Agglomeratic / volcanic breccia – volcanic eruptions

54. Gneiss

55. 12.Gneiss
Gneiss is a metamorphic rock formed by heat or pressure from rocks
of granitic composition. It is somewhat heavier than granite but in
other physical properties, the two rocks are much the same. The
characteristic feature of gneiss is its structure: the mineral grains are
elongated, or platy, and banding prevails. Sometimes gneisses grade
into schists. There is generally less distortion than in the highly foliated
rocks. The weathered residue is gritty with resistant silica particles.
Usually gneisses represent good engineering materials, except for
those with an abundance of mica flakes. These types cannot be used
for building stones because of air-slaking and raveling or for concrete
because of the weakening effect resulting from cleavage. In-situ,
however, gneiss is considered to have good foundation characteristics
and is similar to granite in performance.

56. Schist

57. 13.Schist
Schists may form from number of igneous or sedimentary rocks be
recrystallization when subjected to pressure. They are fine-grained, foliated
rocks which tend to crush to thin and flat fragments. Schists are fairly tough
when tested perpendicularly to the plane of foliation, but if tested parallel with
this plane, the rock may fail readily. Schists are fairly durable and chemically
stable.
Some schists may be composed almost entirely of silica and have an almost
massive structure, depending on the amount of pressure applied in the
metamorphic process. Schist may or may not be a competent material. During
excavation, blocks may separate along planes of foliation. If schist is acted upon
by fast-running water, it may require some protection to prevent "quarrying"
(plucking action) by the water. In general the dip of the planes of schistosity in
schists is different from the dip of the whole formation. Both dips are of
importance, since sliding may occur along either dip. This type of dip is also
observed in other platy rocks such as slate. If there is no tendency for sliding,
schist may be a good foundation material. Schists may also be intricately folded
and distorted. Fracturing, softening, weathering, or deep erosion occurs in zones
of intense movement. Weathering produces clayey, micaceous residue.

58. Slate and
Phyllite

59. 14. Slate and Phyllite
Slate is a dark colored, platy rock with
extremely fine texture and easy cleavage.
Because of this easy cleavage, slate is often
split into very thin sheets and used as roofing
material. As foundation material, slate is
excellent; however, in excellent, in excavations,
large slate blocks may suddenly detach when
undermined.
Phyllite, although physically similar to slate,
differs somewhat by a shiny luster imparted
by mica flakes, by more pronounced
brittleness, and by a tendency to air-slake.
Cases of swelling have been observed in
tunnels through phyllites when the pressure
from overburden was relieved by tunnel
excavation

60. 15.Quartzite
Quartzite, a metamorphosed sandstone, is one of the
toughest and most stable of rocks. Its chief objectionable
characteristic is that it crushes to thin and elongated
pieces. Quartzite has been widely used in road
construction with excellent results, provided
consideration is given to excess fragments of poor shape.
Quartzite is very difficult to drill or excavate (hardness 7).

61. Marble

62. 16.Marble
Marble is the end product of the metamorphism of limestone and
other sedimentary rocks composed of calcium or magnesium
carbonate. It is very dense and exhibits a wide variety of colors,
depending upon the impurities present. When the rock is broken, a
highly brilliant (lustrous) surface is apparent because of the large size
of the crystals normally found in marbles. In construction, marble is
used for facing concrete or masonry exterior and interior floors and
walls. It is occasionally used as a road building aggregate, although it
may be inferior to limestone and dolomite in physical strength.
Generally it has engineering characteristics similar to limestone and
dolomite.