The relationship of orthopyroxene to pigeonite

Abstract

Interest in the orthopyroxene series is evidenced by the great number of publications on that subject which appeared in the literature. Correlations of the chemical composition and optical properties were attempted by Winchell (1923, 1933), Walls (1935), Henry (1935), and Hess and Phillips (1940). The nomenclature of the series was discussed by Winchell (1923), Alling (1936), and Hess and Phillips (1940). The obscure phenomena exhibited by certain orthopyroxenes in polarized light, attributed by some to twinning, by others to exsolution, was noted by a great many petrologists, of whom are mentioned here Lewis (1908), Holmes and Harwood (1928), Guimarães (1933), Scholtz (1936), Hess and Phillips (1938, 1940), Kuschke (1939), Wager and Deer (1939), Nel (1940), Walker (1940, 1943), Walker and Poldervaart (1940, 1941), Edwards (1942), Henry (1942), and Poldervaart (1944, 1946).

XRD, SEM and Petrologic Characterization of a L4-L5 Ordinary Chondrite Meteorite

“…25% volume). Spot analyses by EDS in several domains of the largest chondrule show that orthopyroxene has uniform composition with Mg/(Mg+Fe) between 0.77 and 0.79 (enstatite, following the presently adopted pyroxene classification [12]; bronzite, according to the old nomenclature [13]). On the other hand, glass has oligoclase-type composition (Ab 74 to Ab 81 ).…”

The petrography and geochemistry of corona-bearing dolerites from the Jotun Nappe, central southern Norway

“…The clouding of plagioclase and, to a lesser extent, clinopyroxene (probably with iron oxide and, or, spinel), preceded the formation of the coronas, and it is clear that the degree of development of coronas is greatest when the plagioclase and clinopyroxene are most intensely clouded. Poldervaart and Gilkey (1954) regarded such clouding phenomena as being due to the preferential alteration of sub-microscopically unmixed plagiodase by iron-rich fluids. A similar alteration model was proposed by Whitney (1972) and, after a detailed critique, Smith (1974, section 205) also adopted this view.…”