Picrite

picrite

[′pi‚krīt]

(petrology)

A medium- to fine-grained igneous rock composed chiefly of olivine, with smaller amounts of pyroxene, hornblende, and plagioclase felspar.

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 It might be outdated or ideologically biased.

Picrite

 

an effusive rock composed of augite and olivine. Pi-crite also contains admixtures of hornblende, biotite, and or-thopyroxene and of various secondary minerals, including ilmenite, magnetite, and apatite. The olivine is often altered and replaced by serpentine, as well as by iddingsite, chlorite, and sometimes actinolite.

Picrites are holocrystalline. However, they sometimes contain a certain amount of glass inset with augite and olivine (picrite porphyry). The chemical composition of picrites is 38–41 percent SiO₂, 5-10 percent Al₂O₃, and 20-29 percent MgO.

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