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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  • Petrology

    Petrology, the study of rocks. Petrology is a major subdivision of geology and is divided into two main branches: petrography and petrogenesis. See more »

  • Porphyry (rock)
    Porphyry (rock)

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

  • Pumice

    Pumice, a porous, glassy form of lava formed during volcanic explosions. Pumice contains thousands of tiny holes formed by the expansion of gases trapped in the lava as it hardens. See more »

  • Quartzite

    Quartzite, a metamorphic rock derived from sandstone. In some quartzite the sand grains are recemented with silica. See more »

  • Quicksand

    Quicksand, loose or moving fine sand mixed with water. Beneath the sand lies a bed of clay or other impervious material, which prevents the water from draining. See more »

  • Sand

    Sand, small particles of rock and minerals or other materials, such as coral or slag. See more »

  • Sandstone

    Sandstone, a porous sedimentary rock composed of grains of sand usually held together by a natural cement, such as lime. See more »

  • Schist

    Schist, a common metamorphic rock. Schist consists mainly of silicate minerals, chiefly mica, hornblende, talc, or chlorite. See more »

  • Shale

    Shale, the most common type of sedimentary rock. Geologists estimate that between 70 and 83 per cent of the earth's sedimentary rock is shale. See more »

  • Slate

    Slate, a common metamorphic rock that splits into thin, even sheets. Slate consists primarily of such minerals as muscovite (mica), chlorite, and quartz. See more »

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