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.


Marl, a natural mixture of clay and calcium carbonate. It is a loose, earthy substance, usually gray or bluish in color.

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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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