Pyrope

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pyrope

[′pī‚rōp]
(mineralogy)
Mg3 Al2(SiO4)3 A mineral species of the garnet group characterized by a deep fiery-red color and occurring in basic and ultrabasic igneous rocks.

Pyrope

 

a mineral of the garnet group; in pure form, magnesium aluminum garnet Mg3Al2[SiO4]3, containing 20.45 percent MgO and frequent admixtures of Fe, Mn, and other elements. Known for its rich, attractive dark red color, pyrope is a characteristic component of certain peridotites, kimberlites, and serpentinites. Transparent blood-red varieties of pyrope are classed as gems. The most well-known pyropes are from the Czechoslovak Socialist Republic, where they occur in basalt breccia detritus, embedded in peridotites, and are extracted from placers. In the USSR, pyrope occurs in the kimberlites (where pyrope is associated with diamond) and eclogites of the Yakutia.

References in periodicals archive ?
the first batch of pyrope garnets confirm that they were formed in the
The Lakefield Research laboratory and David Petersen, professional engineer and vice president exploration of the company, report that microscopic examination of both drill hole cores has shown the kimberlite to be the peridotite type and to contain all the minerals associated with diamondiferous kimberlites including pyrope-almandine and pyrope garnets (that is, G-9 through G-11 garnets), ilmenite, chrome diopside, phlogopite and spinel in a mass of olivine, pyroxene, calcite and serpentine.
After drilling through loose sand and a thick section of silcrete (Kalahari formation), numerous coarse kimberlitic ilmenites and pyrope garnets of up to 5 mm in size were visually identified in weathered kimberlite from 34 meters depth.
For example, sample Nikos R-04 returned 400 pyrope garnets from just 2.
Pyrope garnets recovered to date from within the Tremblay Corridor consist of 40% G9A or G10A garnets, implying derivation from within the diamond stability window.
All 55 samples contain substantial indicator minerals, including significant pyrope garnets in all but 13 of the samples.
Limited diamond indicator sampling was carried out in 2001 which recovered mantle derived pyrope garnets, chrome diopsides and picro-ilmenites whose chemistry is as good, if not better than the chemistry of these same minerals from the Attawapiskat cluster kimberlites (high chrome, sodium and magnesium substitutions into the crystal fabric), as reported by Ontario Government sampling.
The freshness of many of the grains suggests that their source is nearby and this is supported by the discovery of an angular fragment of kimberlite, containing purple pyrope garnets, in one of the trains.
Encouraging results from the 1992 program consisted of airborne geophysical work and a ground sampling program that resulted in diamond indicator minerals of all seven samples including a total of 106 garnets (31 pyrope garnets of which two are G10 garnets) and five chrome diopsides.
Reconnaissance sampling has detected significant indications of kimberlite minerals including high chrome pyrope garnets (G9 and G10 garnets) high titanium and high sodium eclogitic garnets (G3 and G5 garnets), kimberlitic pyroxenes including abundant chrome diopside and corundum (including both ruby and sapphire).
Encouraging results from the 1992 program consisted of airborne geophysical work and a ground sampling program that resulted in diamond indicator minerals in all seven samples, including a total of 106 garnets (31 pyrope garnets of which two are G10 garnets) and five chrome diopsides.
Pyrope garnets with kelyphite rims were recovered from several samples collected by Dunsmuir and one sample(X02-135) yielded a pyrope garnet with a kimberlite mantle.