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Quartz

  Quartz   Quartz is hexagonal and commonly occurs as crystals ranging in size form microscopic to crystals weighing several tons. Where it crystallizes unhindered by other crystals, such as in cavities in rock or in a liquid containing few other crystals, it shows well-developed hexagonal prisms and sometimes showing apparent hexagonal pyramids or dipyramid. When it crystallizes in an environment where growth is inhibited by the surroundings, it rarely show crystal faces. It is also found as microcrystalline masses, such as in the rock chert, and as  fibrous masses, such as in chalcedony. Vitreous lusture.   As visible crystals, Quartz is one of the more common rock forming minerals. It occurs in siliceous igneous rocks such as volcanic rhyolite and plutonic granitic rocks. It is common in metamorphic rocks at all grades of metamorphism, and is the chief constituent of sand. Because it is highly resistant to chemical weathering, it is found in a wide varie...
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DARWAR SUPER GROUP

 

DARWAR SUPER GROUP 

THE ARCHAEN ROCK SYSTEM – DARWAR SUPER GROUP

THEY ARE BEST DEVELOPED IN SITSES OF KARNATAKA AND THE ADJOINING  STATES

THE SEDIMENTARY OF THE DARWAR GROUP ARE DEPOSITED IN THE BASEMENT OF THE ”FUNDAMENTAL GNEISSES COMPLEX ”

LITHOLOGY :

·         THE CHIEF ROCK TYPE IN THE DARWAR GROUP IS GNEISSES AND GRANITES

·         THEY COVER THE MAJOR PART OF SOUTH INDIA

·         MANY ELONGATED BELTS OF SCHISTOSE ROCKS ARE ENCLOSED WITHIN THESE ROCKS

·         THE SCHISTOSE ROCKS ARE FOLDED ISOCLINALLY AND EXHIBITED A STEEP DIP TOWARDS THE EAST

CLASSIFICATION :

·         IGNEOUS INTRUSION  = (FELCITE AND PHORPYRIC GROUP , CHARNOCHITE , CHAMPIAN GNEISS , PENINSULAR GNEISSCLOSEPET GRANITE )

·         UPPER DARWAR    = FERRUGINIOUS QUARTZITE , LIMESTONE , CONGLOMERATE , QUARTZITE , CALCARIOUS SILTS.

·         MIDDLE DARWAR  =GRANITE ROCK WITH GNEISSOSSE STRUCTURE ,QUARTZITE , CONGLOMERATE , LIMESTONE , CHLORITE SCHIST ,SERISITE SCHIST , BANDED – HEMATITE ,  

·         LOWER DARWAR   = MICASEOUS QUARTZ AND SCHIST  , GREENSTONE – HORNBLENDE – SCHIST

                                    EXPLAINATION OF THREE DARWARS

IGNEOUS INTRUSION :

Ø  CHAMPIAN GNEISSES : CHAMPION GNEISSES IS A SHEARED MICASEOUS GNEISSES, IT IS CHARACTERISTICED BY THE OPALACENT QUARTZ AAND GRAISH TINT

Ø  PENINSULAR GNEISSES : PENINSULAR GNEISS WHICH IS MOSTLY COMPRISED OF GRANITE AND GRANITE GNEISSES , WHICH COVER THE MOST PART OF SOUTH INDIA , PENINSULAR GNEISSES  ARE YOUNGER THENN THE CAMPION GNEISSES

Ø  CHARNAKITE : IT IS A COARSE GRAINED GRAINED GNEISOES ROCK AND HYPERSTHENE THEY RANGE IN COMPOSITION OF ACID AND ULTRA BASIC

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