Some facts about igneous rocks include that they are glassy in nature, that pumice igneous rock is the lightest type of rock on Earth, and that the moon is made of igneous rocks. Igneous rocks come from molten magma and ... More » Science Earth Science Geology

Rock is the primary component of the Earth's crust. Although soil, sand and other natural materials are similar to rocks, they are not actually rocks and are classified as derivatives of rocks. Minerals are necessary to ... More » Science Earth Science Geology

A mineral is made up of one or more elements, such as iron or gold, that are fused together. A rock is classified as igneous, sedimentary or metamorphic based on how it was formed. More » Science Earth Science Geology
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A fine-grained igneous rock is a rock that is formed by melted magma cooling so quickly at the surface of the Earth that only tiny crystals form, most too small to be seen with the naked eye. Basalt is an example of such... More » Science Earth Science Geology

The specific type of rock that forms when magma cools at the Earth's surface is extrusive igneous rock. Igneous rock forms when magma cools, but where the magma cools determines the type of igneous rock that forms. Igneo... More » Science Earth Science Geology

Mafic, or basaltic, igneous rocks contain a greater portion of iron and magnesium than silica, and they are often much darker in color, typically black, dark brown or dark gray, compared to the lighter-colored igneous ro... More » Science Earth Science Geology

Porphyritic rock is a texture of igneous rock with two distinctly different crystal sizes due to two periods of cooling occurring at different rates. Larger crystals are called phenocrysts, while the smaller grains are k... More » Science Earth Science Geology