Foidolite

Foidolite (/ˈfɔɪdəlaɪt/) is a rare phaneritic (coarse-grained) intrusive igneous rock in which more than 60% (by volume) of light-coloured minerals are feldspathoids.^[1] Crystals of alkali feldspar, plagioclase, biotite, amphibole, pyroxene, and/or olivine may be present within the rock. The volcanic equivalents are termed foidite and phonolitic or tephritic foidites.

Foidolite (sodalitolite variety) from Namibia

Thin section of foidolite under polarizing microscope. In the foreground there is a large yellow sodium pyroxene grain surrounded by fine grains.

Some foidolites are a potential source of aluminium.

See also

• QAPF diagram