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 ?
The rock is medium to coarse grained and consist of quartz, alkali feldspar and plagioclase as major mineral however, muscovite, biotite, tourmaline, epidote and apatite are also present in minor quantities.
(1) Hydro thermal alteration event in a early mineralization stage observed in the contact of quartz veins and host rocks, which has fine-grained pyrite, sencite, and quartz with mosaic texture and is associated with fine-grained calcite, chlorite and epidote.
Epidote, quartz, muscovite, H/L and clay were accessory minerals.The complete characterization of the originally employed historic materials also provided information on the techniques, which should be respected for successful restoration programs.
The 2 cases from one mineralized sheet include mineralization of malachite, magnetite and epidote that has a thickness about 2.5 meter and length of 22 meters and extended in line with N70E degree and steep of 85degree in line with the limestone layer.
Non-metallic minerals are apatite, quartz, hornblende, actinolite, epidote, chlorite, Saussure, pomegranate.
In most of the cases, but especially in the rocks of intermediate to acid composition, the rocks show moderate to severe hydrothermal alteration, with the development of potassic minerals (sericite, K-feldspar), prehnite, and carbonates accompanied by other secondary minerals (epidote, quartz, chlorite, titanite).
The first stage of alteration includes Na-Ca metasomatism (actinolite + titanite + epidote + calcite + albite [+ or -] scapolite [+ or -] quartz), which is characteristic of diorite-monzodiorite plutonic rocks (Figure 6(a)).
Pakistan is blessed with vast natural reserves of precious, semi-precious and coloured gemstones, including ruby, sapphire, emerald, tourmaline garnet, topaz, peridot, aquamarine, spinel, pargasite, diopsite, moonstone, serpentine, jade, epidote, pink beryl (morganite), goshnite, sphene, zoisite, turquoise, epitite, agite and almost all known varieties of quartz.