Rocks
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In geology, a rock is a naturally occurring solid aggregate of one or more minerals or mineralogical.Rocks have been used by mankind through out history. From the Stone Age rocks have been used for tools. The minerals and metals we find in rocks have been essential to human civilization.Three major groups of rocks are defined: igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is an essential component of geology.
Sedimentary Rock
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A sedimentary rock is one made up of particles of minerals that have settled out of water or wind in layers that have been subsequently lithified. Think of mud settling at the bottom of a lake, this is a sedimentary deposit.
Igneous Rock
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Igneous rocks (from the Greek word for fire) form from when hot, molten rock (magma) crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface. Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies.
Metamorphic Rock
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Metamorphic rocks are pre-existing rocks that have been changed by exposure to unusual temperatures and/or pressures. The pre-existing rocks, called protoliths, may be igneous, sedimentary or other metamorphic rocks. After metamorphosis, these new rocks typically contain distinctive new minerals, reoriented into characteristic patterns. Metamorphic rocks are very common in the Jacksonville area and throughout the entire Appalachian mountain chain, so a knowledge of these rocks is essential.