felsicos

Felsicos is a term used in geology to describe rocks and minerals that are rich in light-colored silicate minerals and have relatively high silica content. In many languages, including Spanish, felsicos corresponds to the English term felsic. The concept groups materials with similar mineralogy and physical properties, typically contrasting with mafic rocks that are richer in magnesium and iron.

Characteristic minerals include quartz and feldspars—both alkali feldspar and plagioclase—and often mica such as muscovite. Ferromagnesian minerals are relatively scarce in felsics. This mineral assemblage yields light-colored rocks with lower density than mafic rocks and relatively high viscosity magmas.

Common felsic rocks include granite and granodiorite in plutonic settings, and rhyolite and obsidian in volcanic settings. Felsic magmas form by partial melting of continental crust or by differentiation of more mafic magmas; they crystallize at lower temperatures, contributing to the light color and coarse or intermediate textures of felsic rocks.

Felsic rocks are widespread in the continental crust and are economically important as sources of quartz and feldspar for glassmaking, ceramics, and other industrial uses.