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a. A group of chiefly magnesium-iron minerals including diopside,
hedenbergite, augite, pigeonite, and many other rock-forming minerals.
Although members of the group fall into different systems (orthorhombic,
monoclinic, and triclinic), they are closely related in form, composition,
and structure. See also: acmite;
aegirite;
augite; diallage;
enstatite;
hypersthene. Fay; AGI
b. The mineral group aegirine (Ae), aegirine-augite, clinoenstatite,
clinoferrosilite, diopside (Di), donpeacorite, enstatite (En), essenite
(Es), ferrosilite (Fs), hedenbergite (Hd), jadeite (Jd), jervisite (Je),
johannsenite (Jo), kanoite (Ka), kosmochlor (Ko), natalyite, omphacite,
petedunnite (Pe), pigeonite, and spodumene (Sp). Some former names
relegated to synonyms include acmite = aegirine, bronzite = enstatite,
clinohypersthene = clinoenstatite or clinoferrosilite, diallage = altered
diopside or other pyroxene with good (100) parting, eulite = ferrosilite,
fassaite = ferrian aluminian diopside or augite, ferroaugite = augite,
ferrosalite = hedenbergite, hiddenite = spodumene, hypersthene = enstatite
or ferrosilite, kunzite = spodumene, salite = diopside, titanaugite =
titanian augite, uralite = pseudomorphous amphibole after pyroxene, and
ureyite = kosmochlor. Pyroxenes (px) are either monoclinic
(clinopyroxenes, cpx) or orthorhombic (orthopyroxenes, opx). General
formula: AB2 ZO6 : A = Ca, Fe2+ , Li, Mg, Mn (super
2+) , Na, Zn; B = Al, Cr3+ , Fe2+ , Fe3+ , Mg,
Mn2+ , Sc, Ti, V3+ ; Z = Al, Si. Their structures are
built from single chains of silica tetrahedra each sharing two oxygens,
with a silica: oxygen ratio of 1: 3, electrostatic neutrality being
maintained by cross-linking cations. Crystals are prismatic with prismatic
cleavage at 87 degrees and 93 degrees . Colors are mostly greens, but
range from white to black. Etymol: Greek pyros (fire) + xenos (stranger)
from a mistaken belief that they were only accidently caught up in lavas.
See also: aegirine
Source:
Dictionary of Mining, Mineral, and Related Terms
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