Aphanitic rocks

thumb|Diabase

Basanite () is an igneous, volcanic (extrusive) rock with aphanitic to porphyritic texture. It is composed mostly of feldspathoids, pyroxenes, olivine, and calcic plagioclase and forms from magma low in silica and enriched in alkali metal oxides that solidifies rapidly close to the Earth's surface.

thumb|The smooth texture of this basaltic [[volcanic bomb is aphanitic.]] thumb|upright=1.3|IUGS classification of aphanitic extrusive [[igneous rocks according to their relative alkali (Na2O + K2O) and silica (SiO2) weight contents. Blue area is roughly where alkaline rocks plot; yellow area where subalkaline rocks plot.]] thumb|An aphanitic volcanic sand grain, with fine-grained matrix (geology)|groundmass, as seen through a [[petrographic microscope]]

right|thumb|A sample of rhyodacite from Slovakia Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from rapid cooling of lava relatively rich in silica and low in alkali metal oxides.

Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii.

variety of high-magnesium olivine basalt that is very rich in the mineral olivine

Mugearite () is a type of oligoclase-bearing basalt, comprising olivine, apatite, and opaque oxides. The main feldspar in mugearite is oligoclase.

type of volcanic rock