typeigneous

Typeigneous is not a standard term in geology. In most scientific usage, the topic is igneous rocks, which form by the cooling and solidification of molten material. The phrase “igneous types” is commonly used to refer to the classification of these rocks by texture and mineral composition.

Igneous rocks originate from magma that crystallizes below the surface (intrusive or plutonic) and from lava that erupts onto the surface (extrusive or volcanic). Cooling rate controls texture: slow cooling yields coarse-grained phaneritic rocks such as granite and diorite; rapid cooling yields fine-grained aphanitic rocks like rhyolite, andesite, basalt; very rapid cooling can produce volcanic glass such as obsidian; partial crystallization can produce porphyritic textures with large crystals in a finer matrix.

Composition classes range from felsic to ultramafic. Felsic and intermediate rocks are rich in silica and light-colored minerals like quartz and feldspar, whereas mafic rocks are richer in magnesium and iron and typically display darker colors (examples include basalt, andesite, and gabbro). Ultramafic rocks, such as peridotite, are even richer in olivine and pyroxene and are more common in the mantle than in exposed crust.

Common examples include felsic granitic rocks (granite, granodiorite), intermediate rocks (diorite, andesite), mafic rocks (basalt, gabbro), and felsic-extrusive equivalents (rhyolite, obsidian) along with vesicular pumice. The igneous classification also reflects tectonic setting and magmatic differentiation processes such as fractional crystallization and partial melting, which produce the diversity of igneous rocks observed on Earth.