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