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.

Porphyry (rock)

Porphyry, any igneous rock consisting of large crystals in a mass of much smaller crystals.

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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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