Phonolite
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phonolite
[′fō·nə‚līt] (petrology)
A light-colored, aphanitic rock of volcanic origin, composed largely of alkali feldspar, feldspathoids, and smaller amounts of mafic minerals.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
Phonolite
(from the Greek phone,”sound,” and lithos,”stone”), the extrusive equivalent of nepheline syenite. Phonolite consists of feldspathoids (nepheline and other rocks), sanidine, and chromatic minerals (alkaline pyroxene and amphibole). It often contains phenocrysts of hauynite, noselite, and, sometimes, plagioclase. Its texture is usually porphyritic. The cleavage is laminar; individual plates of phonolite ring strongly when struck with a hammer (hence the name). Phonolite is used as gravel in road paving and as an aggregate for concrete.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.