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Definition: phonolite from The Macquarie Dictionary

a fine-grained volcanic rock composed chiefly of orthoclase and nepheline, some nepheline varieties of which split into pieces which give a ringing sound on being struck.

(plural phonolites)

phonolitic /foʊnə'lItIk/ /fohnuh'litik/ adjective


Summary Article: Phonolite from Rock and Gem

PHONOLITE IS A TYPE OF TRACHYTE (see here) that contains nepheline or leucite rather than quartz. They are commonly fine grained and compact, and split into thin, tough plates, which make a ringing sound when struck, hence the rock’s name. The principal dark-colored mineral is pyroxene, usually in the form of aegirine or augite. Phonolites are common in Europe, especially on the Eifel plateau and the Laacher See, Germany; in the Czech Republic; and in the Mediterranean area, particularly in Italy. In the USA phonolites are found in Colorado, and the Black Hills, South Dakota. The spectacular Devil’s Tower, Wyoming, is probably phonolite’s most famous occurrence (see Trachyte).

  • Properties
  • Rock type Intermediate, volcanic, igneous
  • Major minerals Sanidine, oligoclase
  • Minor minerals Feldspathoids, hornblende, pyroxene, biotite
  • Color Medium gray
  • Texture Fine to medium, porphyritic

Cripple Creek, USA

Phonolite is found at Cripple Creek, In the Pike’s Peak area of Colorado, USA.

© 2008 Dorling Kindersley Limited

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