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Rocks: Rocks are a composed of one or more minerals. A rock can be made up of only one mineral or, as shown in the figure, a rock can be made up of a number of different minerals. So, rocks are composed of one or more minerals and minerals are composed of one or more elements. Previous Item: Why should we study rocks? Go Up: Learn About Rocks
Igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material. Igneous rocks comprise one of the three principal classes of rocks, the others being metamorphic and sedimentary. 1  Igneous rocks are formed from the solidification of magma, which is a hot (600 to 1,300 Â°C, or 1,100 to 2,400 Â°F) molten or partially molten rock material. The Earth is composed predominantly of a large mass of igneous rock with a very thin veneer of weathered materialânamely, sedimentary rock.