foidolite
Sign in to savethumb|Foidolite (Sodalite|sodalitolite variety) from Namibia thumb|Thin section of foidolite under polarizing microscope. In the foreground there is a large yellow sodium pyroxene grain surrounded by fine grains.
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thumb|Foidolite (Sodalite|sodalitolite variety) from Namibia thumb|Thin section of foidolite under polarizing microscope. In the foreground there is a large yellow sodium pyroxene grain surrounded by fine grains.
Foidolite () is a rare phaneritic (coarse-grained) intrusive igneous rock in which more than 60% (by volume) of light-coloured minerals are feldspathoids. 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.
Excerpted from Wikipedia’s “foidolite” article, available under the CC BY-SA 4.0 licence.