Quartz is a compound of one part silicon and two parts of oxygen, silicon dioxide, SiO2. It is prominently found in Brazil, but there are smaller deposits found in Guatemala, Columbia, and within the United States.
source:http://www.mindat.org/min-3337.html
There are 3 major types of rocks:
Igneous rocks-created by the cooling of original materials, igneous rocks can be created extrusively (above ground) or intrusively (below the ground). An example of igneous rock would be granite, which is created from a blend of quartz, feldspar and hornblende. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth's crust.
source: http://en.wikipedia.org/wiki/Igneous_rock
Their chemical makeup relies on several components.
For instance, they can be:
- felsic igneous rocks containing a high silica content, greater than 63% SiO2 (examples granite and rhyolite)
- intermediate igneous rocks containing between 52 - 63% SiO2 (example andesite and dacite)
- mafic igneous rocks have low silica 45 - 52% and typically high iron - magnesium content (example gabbro and basalt)
- ultramafic rock igneous rocks with less than 45% silica. (examples picrite, komatiite and peridotite)
- alkalic igneous rocks with 5 - 15% alkali (K2O + Na2O) content or with a molar ratio of alkali to silica greater than 1:6. (examples phonolite and trachyte)
source:http://en.wikipedia.org/wiki/Granite
Metamorphic rocks-arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat and pressure, (temperatures greater than 150 to 200 °C and pressures of 1500 bars[1]) causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic rock.
An example of a metamorphic rock would be marble, which is a non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is most commonly found in mountainous areas all over the world...in particular, Italy, China, Turkey and Mexico, but also in Belgium, France, Great Britain, Spain, India, and in many parts of the United States, such as Vermont, Colorado, Tennessee and Alabama.
source: http://en.wikipedia.org/wiki/Marble
http://wiki.answers.com/Q/Where_is_marble_found
Sedimentary rocks- are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to precipitate from a solution. Particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents of denudation. Simply put, sediment becomes a rock by being compacted together. Limestone, which becomes marble when it undergoes metamorphosis.
source: http://www.dep.state.fl.us/geology/geologictopics/rocks/ocala_limestone.htm
http://en.wikipedia.org/wiki/Sedimentary_rock
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