Augite

Augite

Infobox mineral
name = Augite
category = Silicate mineral
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formula = (Ca,Mg,Fe)SiO3
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color = Pale brown to purplish or greenish brown, also dark grey sometimes
habit =
system = Monoclinic
twinning =
cleavage = {110} good
fracture = uneven
mohs = 5 to 6.5
luster = Vitreous
refractive = α = 1.671 - 1.735, β = 1.672 - 1.741, γ = 1.703 - 1.774
opticalprop =
birefringence =
pleochroism =
streak = Greenish-white
gravity = 3.19 - 3.56
density =
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fusibility =
diagnostic =
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Augite is a mineral described chemically as (Ca,Mg,Fe)SiO3 or calcium magnesium iron silicate. The crystals are monoclinic and prismatic. Augite has two prominent prismatic cleavages, meeting at angles near 90°.

Augite is a solid solution in the pyroxene group. Diopside and hedenbergite are important endmembers in augite, but augite can also contain significant aluminium, titanium, and sodium and other elements. The calcium content of augite is limited by a miscibility gap between it and pigeonite and orthopyroxene: when occurring with either of these other pyroxenes, the calcium content of augite is a function of temperature and pressure, but mostly of temperature, and so can be useful in reconstructing temperature histories of rocks. With declining temperature, augite may exsolve lamellae of pigeonite and/or orthopyroxene. There is also a miscibility gap between augite and omphacite, but this gap occurs at lower temperature and is not well understood.

It is found in igneous rocks; for example, gabbro and basalt. It also occurs in relatively high-temperature metamorphic rocks such as mafic granulite.

Occasional specimens have a shiny appearance that give rise to the mineral's name, which is from the Greek "augites", meaning "brightness", although ordinary specimens have a dull (dark green, brown or black) finish.

References

* Deer, W. A., Howie, R. A., and Zussman, J. (1992). "An introduction to the rock-forming minerals (2nd ed.)". Harlow: Longman ISBN 0-582-30094-0


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Look at other dictionaries:

  • Augite — Augite[1] Catégorie IX : silicates[2] Au …   Wikipédia en Français

  • augite — ● augite nom féminin (grec augitês) Pyroxène monoclinique, calcique et ferromagnésien, commun dans les basaltes et les gabbros. ● augite (expressions) nom féminin (grec augitês) Augite aegyrinique, pyroxène de composition intermédiaire entre l… …   Encyclopédie Universelle

  • Augite — Au gite ([add] j[imac]t), n. [L. augites, Gr. a ygi ths, fr. a ygh brightness: cf. F. augite.] A variety of pyroxene, usually of a black or dark green color, occurring in igneous rocks, such as basalt; also used instead of the general term… …   The Collaborative International Dictionary of English

  • augite — [ô′jīt΄] n. [L augites < Gr augitēs, a precious stone < augē, sunlight, brightness < IE base * aug , to gleam] any of various dark colored, hard, monoclinic pyroxenes, (Ca, Na) (Mg, Fe, Al) (Si, Al) 2O6, found in basic igneous rocks …   English World dictionary

  • augite — augitic /aw jit ik/, adj. /aw juyt/, n. a silicate mineral, chiefly of calcium, magnesium, iron, and aluminum: a dark green to black variety of monoclinic pyroxene, characteristic of basic rocks. [1780 90; < L augitis a kind of precious stone …   Universalium

  • augite — augitas statusas T sritis chemija apibrėžtis Mineralas. formulė Ca(Mg,Fe,Ti,Al)[(Si,Al)₂O₆] atitikmenys: angl. augite rus. авгит …   Chemijos terminų aiškinamasis žodynas

  • Augite aegyrinique — ● Augite aegyrinique pyroxène de composition intermédiaire entre l augite et l aegyrine …   Encyclopédie Universelle

  • augite — noun Etymology: Latin augites, a precious stone, from Greek augitēs Date: 1804 1. a usually black or dark green mineral that consists of aluminous pyroxene and is found especially in igneous rocks 2. pyroxene • augitic …   New Collegiate Dictionary

  • augite — noun A variety of pyroxene, usually of a black or dark green color, occurring in igneous rocks, such as basalt …   Wiktionary

  • augite — au·gì·te s.f. TS mineral. minerale di colore scuro o nero, costituito da silicato di calcio, magnesio, ferro e alluminio del gruppo dei pirosseni {{line}} {{/line}} DATA: 1817. ETIMO: der. del gr. augē raggio con 2 ite …   Dizionario italiano

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