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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 variety of sedimentary r
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HYDROTHERMAL ORE DEPOSITS

  HYDROTHERMAL ORE DEPOSITS                                                   Figure 1.1 HYDROTHERMAL PROCESS     Concentration by hot aqueous (water-rich) fluids flowing through fractures and pore spaces in rocks.   The fluid temperature ranges from 50 to 500 degree C. These fluid can be the final product of volcanic differentiation or the ground water got heated by contact of magma or chamber.   Hydrothermal deposits are produced when groundwater circulates to depth and heats up either by coming near to the hot igneous body at depth or by circulating to great depth along the geothermal gradient.   Such hot water can dissolve valuable substances throughout a large volume of rock. As the hot water moves into cooler areas of the crust, the dissolved substances are precipitated from the hot water solution. If the cooling takes place rapidly,  T hey might occur in open fractures or upon reaching a body of cool surface water, then precipitation will take place over a limi
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TYPE OF METAMORPHISM

  TYPES OF METAMORPHISM Metamorphism can take place in several environments where special conditions exist like pressure, temperature, stress, conditions, or chemical environments.by this different conditions application  several different types of metamorphism  are :-  Contact metamorphism  Burial metamorphism  Dynamic metamorphism  Regional metamorphism  Hydrothermal metamorphism  Subduction related metamorphism  Shock metamorphism   Contact Metamorphism   ( alias thermal metamorphism) -                                                                               Figure 1.1   Occurs adjacent to igneous intrusions and results from high temperatures associated with the   igneous   intrusion. Since only a small area surrounding the intrusion is heated by the  magma, metamorphism is  restricted to a zone surrounding the intrusion, called a  metamorphic aureole. Outside of the contact  aureole, the rocks are un-metamorphosed.  The  grade of metamorphism increases in all directions  towa
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TYPES OF METAMORPHIC ROCKS

TYPES OF METAMORPHIC ROCKS                                                                       Figure 1.1 There are two major subdivisions of metamorphic rocks :-                                                                  1. Foliated metamorphic rocks                                                                   2. Non foliated metamorphic rocks                                                                                                                            Figure 1.2 ( foliated rock) 1. Foliated – These have a planar foliation caused by the preferred orientation (alignment) of minerals and formed under differential stress. They have a significant amount of sheet silicate (platy minerals and are classified by composition, grain size, and foliation type.2. Non-foliated – These have no evident planar fabric or foliation, crystallized under conditions where there was no differential stress, and are comprised of equant minerals only. These are classified ma
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METAMORPHISM

                                                                  METAMORPHISM                                                              figure 1.1 ( Metamorphosed Quartzite) Definition :-                 The word "Metamorphism" comes from the Greek (Meta = after, morph = form,).So                 metamorphism means the after form. In geology this refers to the changes in mineral                    assemblage and texture that result from subjecting a rock to pressures and temperatures different from those under which the rock originally formed.  The original rock that has undergone metamorphism is called the protolith . Protolith can be any type of rock and sometimes the changes in texture and mineralogy are so dramatic that is difficult to distinguish what the protolith was.   Note that diagenesis and weathering are also a changes in form that occur in rocks. In geology however, we restrict diagenetic processes to those which occur at temperatures below 200° c and p
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ORIGIN OF COAL AND ITS TYPE

                                                   COAL ORIGIN AND ITS TYPES   FIGURE 1.1 ( COAL )   Stratified, compact, mass of plant debris modified chemically and physically by natural       agencies,    Plant debris mainly but not exclusively from terrestrial plants  Natural agencies causing physical and chemical changes: bacteria & fungi, oxidation, reduction,    hydrolysis, condensation; effect of heat and pressure in presence of water    Physical changes: reduction in strength of woody cell structure, development of colloidal     properties, increase in depth and brightness of color, increase in hardness and brittleness    Chemical properties of a coal depends upon properties of the different constituents of the   vegetable matter, the nature and extent of the changes      Inorganic matter proportion in coal is small, oil shales and carbonaceous shales which differ   from coal only in having inorganic matter as their major component, are not classed as coal    Cannel coals
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