femic rock

geology

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 26, 2026

Quick Summary

In geology, mafic rock is a type of igneous rock characterized by a high concentration of magnesium and iron-rich silicate minerals like pyroxene, amphibole, olivine, and mica. These minerals give mafic rocks their dark color, distinguishing them from felsic rocks, which are dominated by lighter-colored minerals.1

Mafic rocks typically contain between 45% and 55% silica. Common examples include basalt, which is extrusive (volcanic), and its intrusive equivalent, gabbro. The term "femic" is often used interchangeably with mafic, also referring to rocks rich in iron and magnesium.2134

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

9 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

igneous rock
Chemical components
…and magnesium (Mg), are termed femic (from ferrous iron and magnesium), whereas the silicic rocks are referred to as sialic (from silica and aluminum, with which they are enriched) or salic (from silica and aluminum). The terms mafic (from magnesium and ferrous iron) and felsic (feldspar and silica) are used…
Read More
…and magnesium (Mg), are termed femic (from ferrous iron and magnesium), whereas the silicic rocks are referred to as sialic (from silica and aluminum, with which they are enriched) or salic (from silica and aluminum). The terms mafic (from magnesium and ferrous iron) and felsic (feldspar and silica) are used…
Read More