orthopyroxene

plural orthopyroxenes

1. chemistryAny pyroxene that forms orthorhombic crystals.

   However, the relatively low Al₂O₃ content of the co-existing orthopyroxenes (2.2 wt%) is not consistent with an upper mantle origin (Binns et al. 1970) and therefore probably crystallised at crustal pressures.

   2011, M. C. Bruce, “Geodiversity of the Southern Barrington Tops Lava Field, New South Wales: A Study in Petrology and Geochemistry”, in M. L. Augee, editor, Proceedings of the Linnean Society of New South Wales, volume 132, page 59

   2 more examples

   Biotite from lava flows is invariably rimmed or totally replaced by an exceedingly fine-grained, almost isotropic intergrowth of K-feldspar, orthopyroxene, cordierite and ilmenite, probably as a result of dehydration of the magma on eruption. Cordierite and orthopyroxene (5% each) occur as euhedral phenocrysts 1 to 2 mm in diameter, but cordierite can be up to 5 mm across and occur as anhedral ovoids.

   1981 November 10, D. Wyborn, B. W. Chappell, R. M. Johnston, “Three S‐Type Volcanic Suites from the Lachlan Fold Belt, Southeast Australia”, in Journal of Geophysical Research, volume 86, number B11, →DOI, →ISSN, page 10337

   The meteorite contains abundant, distinct to poorly defined chondrules (about 40 volume %). They are enclosed in a recrystallised, heavily iron-stained, but coherent matrix of irregular fragments of olivine and orthopyroxene, together with fragmented chrondrules and small grains and interstitial areas of oligoclase.

   1998, William D. Birch, “The Broken Hill Meteorite, New South Wales, Australia”, in Journal and Proceedings of the Royal Society of New South Wales, volume 131, →ISSN, page 96