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THIRD UNIT-PETROLOGY.pptx

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

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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
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
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
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).
GRANITE
GRANITE POLISHED
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.
•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
•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.
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
SYENITE
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
Equigranular, Coarse grained texture,
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.
DIORITE
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.
GABBRO
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.
PEGMATITES
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.
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.
DOLERITE
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
•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
•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
BASALT
•7.BASALT •ESSENTIAL MINERALS •Feldspar – Plagioclase • ( Labradorite) – Only in few cases, Andesine, Oligoclase, Albite. •Monoclinic pyroxene, Augite •Iron oxide •ACCESSORY MINERALS •Illmenite •Magnetite
•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
•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.
•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.
Sandstone
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
•STRUCTURE •Stratification •Current bedding •Ripple marks •Rain prints •Current bedding •Ripple marks •Rain prints •Stratification
•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
•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
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
•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
TRAVERTINE – hot spring CORAL LIMESTONE- organic
ALGAL LIMESTONE
ALGAL LIMESTONE
•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.
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.
9.CONGLOMERATES •Rudaceous group •Rounded fragments of various sizes •Cemented by clayey or ferruginous or mixed matrix. •Roundness: transported considerable distance.
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.
SHALE
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
•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.
Breccia
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
Gneiss
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.
Schist
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.
Slate and Phyllite
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
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).
Marble
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.

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THIRD UNIT-PETROLOGY.pptx

  • 1.
    Rocks are classifiedby 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 areformed 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 areformed 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 areformed 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).
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    1.GRANITE •Plutonic rock body •Holocrystallineand 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.
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    •TEXTURE •Interlocking phaneric Coarsegrained 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
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    •STRUCTURE •Compact dense massivehard 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
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    2.SYENITE •SYENITE – Namedafter 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
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    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.
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    3. DIORITE •Plutonic rocks •Intermediatebetween 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.
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    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.
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    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.
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    DIAGNOSTIC CHARACTERS •Very largesized 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.
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    6.DOLERITE •Dark, heavy, finegrained 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
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    •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
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    •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
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    •7.BASALT •ESSENTIAL MINERALS •Feldspar –Plagioclase • ( Labradorite) – Only in few cases, Andesine, Oligoclase, Albite. •Monoclinic pyroxene, Augite •Iron oxide •ACCESSORY MINERALS •Illmenite •Magnetite
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    •TEXTURE •Vesicular and amygdoloidaltextures; 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
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    •DECOMPOSITION •Olivine show alterationto 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.
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    •ENGINEERING IMPORTANCE OFBASALT •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.
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    8.SANDSTONE •NATURE •Arenaceous •Color depends uponcementing 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
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    •VARIETIES •ORTHOQUARTZITE – siliceoussandstone 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
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    •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
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    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
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    •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
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    TRAVERTINE – hotspring CORAL LIMESTONE- organic
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    •ENGINEERING IMPORTANCE •Massive andcompact 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.
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    Conglomerate Conglomerate rocks aresedimentary 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.
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    9.CONGLOMERATES •Rudaceous group •Rounded fragmentsof various sizes •Cemented by clayey or ferruginous or mixed matrix. •Roundness: transported considerable distance.
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    TYPES OF CONGLOMERATE •Basalconglomerates •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.
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    10.SHALE •NATURE •ARGILLACEOUS •Color variable •Soft scratchedby 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
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    •ENGINEERING IMPORTANCE •Laminated sedimentaryrocks •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.
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    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
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    12.Gneiss Gneiss is ametamorphic 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.
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    13.Schist Schists may formfrom 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.
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    14. Slate andPhyllite 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
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    15.Quartzite Quartzite, a metamorphosedsandstone, 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).
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    16.Marble Marble is theend 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.