Phonolite
Phonolite is an
igneous, volcanic (
extrusive)
rock, of felsic composition, with
aphanitic to
porphyritic texture. Mineral assembly is usually abundant feldspatoids and alkali
feldspar, and lesser
plagioclase.
Biotite, amphiboles and
pyroxene are common accessory minerals.
Quartz is absent.
Some phonolite outcrops make a musical sound when struck -- hence the name.
See also: igneous rocks, list of rocks