Petrology is a discipline of geology that studies rocks, minerals and the processes that act on them. Scientists focus on the formation of rocks in this field of science.


Rock, the solid material that makes up the earth's crust. Soil, sand, and other loose natural materials are not usually considered to be rock, although they are derived principally from rocks.

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  • Travertine


    Travertine, a soft, compact or porous form of limestone. It is usually pale yellow, but may be dark yellow, brown, or streaked with light and dark bands because of impurities. See more »

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