Foyaite

foyaite

[′fȯi·yə‚īt]

(petrology)

A nepheline syenite composed chiefly of potassium feldspar.

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 It might be outdated or ideologically biased.

Foyaite

 

(named after La Foia, a peak in the Serra di Monchi-que, in southern Portugal), a leucocratic, completely crystalline intrusive rock; an aegirine or hornblende variety of nepheline syenite. Foyaites consist of about 60 percent potassium feldspars, usually microcline-perthite and orthoclases, about 25–30 percent nepheline, and about 10 percent colored minerals, such as aegi-rine-augite, alkaline hornblende, and, very rarely, iron biotite. Foyaites usually contain ore minerals, titanite, apatite, and zircon. They are widely distributed in various alkaline rock complexes. Foyaite is used as a construction material.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.