Mafic is an adjective describing a silicate mineral or igneous rock which is rich in magnesium and iron. The term is a portmanteau, made up from "magnesium" and "ferric".

Mafic minerals are usually dark in color and have a specific gravity greater than 3. Common rock-forming mafic minerals include olivine, pyroxene, amphibole, biotite and other micas, augite and the calcium-rich plagioclase feldspars. Common mafic rocks include basalt and gabbro.

In terms of chemistry, mafic rocks are on the other side of the rock spectrum from the so-called felsic rocks. The term roughly corresponds to the older basic rock class.

Mafic lava, before cooling, has a lower viscosity than felsic lava due to its lower silica content. Water and other volatiles can more easily and gradually escape from mafic lava, so eruptions of volcanoes made of mafic lavas are less explosively violent than felsic lava eruptions. Most mafic lava volcanoes are oceanic volcanoes, like Hawaii.

Rock TextureName of Mafic Rock
PegmatiticGabbro pegmatite
Coarse grained (phaneritic)Gabbro
Coarse grained and porphyriticPorphyritic gabbro
Fine grained (aphanitic)Basalt
Fine grained and porphyriticPorphyritic basalt
PyroclasticBasalt tuff or breccia
VesicularVesicular basalt
AmygdaloidalAmygdaloidal basalt
Many small vesiclesScoria
GlassyTachylyte, sideromelane, palagonite
  • related pages

Related pages

Other Languages
Afrikaans: Mafies
العربية: صخر مافي
български: Мафичен
català: Màfic
čeština: Mafity
English: Mafic
español: Máfico
euskara: Mafiko
فارسی: مافیک
français: Mafique
Bahasa Indonesia: Mafik
íslenska: Basísk kvika
italiano: Femico
עברית: מאפי
ქართული: ფუძე ქანები
Nederlands: Mafisch
日本語: 苦鉄質
norsk nynorsk: Mafiske mineral
português: Máfico
slovenčina: Mafický
slovenščina: Mafičnost
српски / srpski: Мафичност
suomi: Mafinen
Türkçe: Mafik
Tiếng Việt: Mafic
吴语: 铁镁质
中文: 铁镁质