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.

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.

References in periodicals archive ?
One of the rocks that has been studied as a potential source of K is the volcanic phonolite found in Pocos de Caldas, MG, Brazil, which presents 8.0% of total [K.sub.2]O.
Phonolites are characterized by phenocrysts of leucite-pseudomorphs, alkali feldspar ([Or.sub.47-75]), clinopyroxene ([Wo.sub.48-50][Fs.sub.11-34]), Fe-pargasite, and nepheline [+ or -] biotite [+ or -] titanite [+ or -] melanite (Ti-andradite up to 68 wt%) [+ or -] magnetite or haematite.
Andreas also had nice little specimens of tuperssuatsiaite from the Aris Phonolite; lovely deep green Erongo Mountains fluorite across a range of sizes; a couple of the elusive grossular crystals from Marienfluss, and many other Namibia goodies.
The investigated screes are formed by andesite, basalt, conglomerate, limestone, phonolite, quartzite, sandstone, granite and other kinds of rock.
Novak J.K., Melka K., Ulrych J., Randa Z.: Phonolite Weathering Profiles at Marianske Hora Hill, Ceske Stredohori Mts., and Sorption Properties of Clay Residues
Similar position of the sodalite pheno-crysts has been reported from zeolitized phonolite of the Marianska hora Hill (Ulrych et al., 2000).
1997 From alkali basalt to phonolite in hand-sized samples: vapor-differentiation effects in the Bouzentes lava flow (Cantal, France).
The most intriguing of these was a find, this past summer, of gemmy orange villiaumite crystals from the Aris phonolite quarry.
Some of the weathered phonolite bodies, buried beneath the Most Basin and covered by Miocene sediments, have been studied in open cast lignite mines.
Three reference suites from Iceland, Moorea and Tristan da Cunha illustrate (respectively) the tholeiitic series containing basalt to rhyolite, the alkaline series with alkali basalts to trachytes and a strongly alkaline series, beginning with basanite and ultimately yielding phonolite; few oceanic islands contain tholeiiteseries rocks.
Ninety species have been documented from the quarry, mostly from the unique, dawsonite-rich carbonatized phonolite sills which are genetically part of the Monteregian Hills alkaline igneous province.