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 »

The most common type of igneous rock, basalt, also known as malfic rock, can be found on oceanic plates at divergent plate boundaries. Intermediate and felsic igneous rocks show up along continental margins, as well. Bec... More »

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 »

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 »

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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 »

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 »

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 »