Epidote


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epidote

[′ep·ə‚dōt]
(mineralogy)
A pistachio-green to blackish-green calcium aluminum sorosilicate mineral that crystallizes in the monoclinic system; the luster is vitreous, hardness is 6½ on Mohs scale, and specific gravity is 3.35-3.45.

Epidote

 

a rock-forming mineral of the silicate class, with chemical composition Ca2[Al, Fe, Mn]3[SiO4][Si2O7]O(OH). Epidote crystallizes in the monoclinic system, often forming well-faceted, elongated prismatic crystals. It also occurs in the form of granular, divergent, or parallel columnar aggregates. It has a perfect cleavage and a vitreous luster. Its hardness on Mohs’ scale is 6–7. Its density increases from 3,300 to 3,450 kg/m3 with increasing iron and manganese content. The color of epidote is related to inclusions of ions of transition metals in the structure and varies from colorless or bluish gray (for clinozoisites, which do not contain Fe and Mn) to dark green (for large concentrations of Fe). Epidote with a high Mn content, called piedmontite, has a pink or red-brown color.

Epidote is a typical mineral of limestone skarns, as well as of low- and medium-temperature metamorphic rocks rich in Ca. Experimental study of certain important chemical reactions between epidote and other silicates (garnet and anorthite) has made it possible to use epidote as an indicator of the physicochemical conditions of the formation of the rocks in which it is found.

REFERENCE

Kepezhinskas, K. B., and V. V. Khlestov. Statisticheskii analiz mine-ralov gruppy epidota i ikhparageneticheskie tipy: Moscow, 1971.

L. IA. ARANOVICH

References in periodicals archive ?
Quartz (10%) forms heteroblastic and xenoblastic individuals; it presents inclusions of titanite, clinozoisite and epidote.
Micro-veins of epidote and of calcite traverse the rocks sparingly.
In the ZMT--336 samples that is harvested from Zone Skarn are mineral garnet, plagioclase, epidote along with diopcide in the background of rock in the strip form of diopcide and epidote minerals.
The first one corresponds to epidote-amphibolite facies, represented by hornblende + epidote group minerals + quartz + albite [+ or -] garnet (Figure 3c).
11 membres des OMLT (equipes de liaison et de tutorat operationnel encadrant l'armee afghane), dix de la mission Epidote, chargee de la formation de l'armee afghane, et un membre de l'etat-major doivent partir avec eux.
The hydrothermal system consists of clay alteration, widespread zones of limonitization, structurally controlled extensive quartz veins, frequently occurring manganese oxides and galena, little pyrite and epidote.
The chargeability zone is also a strong alteration feature with peripheral volcanic rocks altered to chlorite and epidote (propylitic alteration) and the mineralised zone containing higher grade biotite alteration suggesting proximity to a mineralised source.
Most notable among these was the epidote from the Lola claim and topaz, smoky quartz and amazonite from the Zapot claim, both near Hawthorne.
The gneiss consists of alternating amphibole + plagioclase and epidote + quartz layers.
Higher grade rocks contain actinolite and epidote indicative of greenschist- facies conditions.
The MPH sample was dominated by diopside and hornblende; RSB by epidote, garnet, and biotite; and SQB by rutile, epidote, staurolite, and apatite.