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PETROLOGY Petrology is the study of rocks and describes many different types yielded by three major processes of rock formations: Ingenious, sedimentary, and metamorphic. Ingenious Rocks They Comprise more than ninety per cent of the earth’s crust. Ingenious means fiery in Latin and so describes how these rocks are formed. Sometimes they are also known as magmatites. They can be divided into two types; vulcanite, which are volcanic minerals of volcanic origin and plutonite which are formed underground when the lava flow does not escape from the surface and settles in a void in the crust. This huge rock is termed a batholith. The substances in the magma form the different minerals and crystals together with the forces of pressure, temperature and time. Crystals formed from volcanic eruption, (extrusive), are often small because of the rapid cooling and lack of pressure and time. Examples of these are; porphyrite, rhyolite, olivine, rose quartz and zircon. The intrusive ingenious rocks or plutonites which have millions of years at their disposal and are under pressure can form much larger crystals, examples of which are; aventurine, aragonite, fluorite, kunzite, moonstone (hydrothermal), agate, amethyst, clear and smokey quartz and chalcedony. Sedimentary Rocks. The earth’s continental crust is constantly exposed to the changing weather conditions of rain, wind, frost, sunshine and storms. It is also affected by shifting. The rocks get broken up and find their way into lower plains, deltas, lakes, rivers and oceans and are gradually eroded into small pebbles, sand or silt. Often layers are formed where the upper mass exerts a pressure on the lower deposits. New minerals develop and these grow over time. Examples of these are; angelite, calcite, dolomite, selenite, pyrite, boji stones, azurite, malachite, chrysocolla, dioptase, turquoise, silver and copper.
Approximate Word count = 1156
Approximate Pages = 4.6
(250 words per page double spaced)
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