Igneous rocks form from the cooling and solidification of molten rock. This molten material, called magma when it stays below the surface, and lava when it erupts onto the surface, originates deep in the Earth and rises because of partial melting and differentiation processes. As the molten material cools, its minerals crystallize to create igneous rocks. The rate and setting of cooling determine texture and crystal size, giving rise to two main categories: intrusive (plutonic) rocks that crystallize slowly beneath the surface and are typically coarse-grained, and extrusive (volcanic) rocks that erupt or erupt nearby and cool rapidly to form fine-grained textures or volcanic glass. Common intrusive igneous rocks include granite, diorite, and gabbro, while common extrusive examples include rhyolite, andesite, basalt, obsidian, and rhyolite. The composition of igneous rocks is broadly classified as felsic (silica-rich, light-colored minerals like quartz and feldspar) or mafic (silica-poor, richer in magnesium and iron), with intermediate and ultramafic varieties forming along this spectrum.