Discovery of Pyrope Spessartite garnets ( Madagascar )

Written by Alain Darbellay GGGems


© 2004 gggems.com All rights reserved.

A day of July 1996 whereas I stopped in a small village in Madagascar, one presented samples of a strange stone to me. At first sight its color could reminds certain zircon, but I quickly identified them as garnet. After some palaver, one led me torepparttar place ofrepparttar 109297 discovery. I must acknowledge that I already knewrepparttar 109298 inhabitants with whom I tied friendshiprepparttar 109299 previous year. Onrepparttar 109300 spot, a notch of about one meter fifty in a white color rock had created a not very impressive hole. But, according to its authors, it was particularly painful to produce it with iron bars only . I readily believed them after to be approached torepparttar 109301 rock. Some particles of this stone torepparttar 109302 orange - pink-brown reflections remained taken inrepparttar 109303 bedrock. I encouraged my friends to be still sought. The first samples extracted from a not disaggregated leptynite did not exceed 3.15 cts. after cutting. The observation under day light and incandescent light showed a clear difference in color. Its change, fromrepparttar 109304 champagne color under daylight, to an intense red for some, or to pink-orange for others is due to chromium and vanadium traces. This characteristic confers an attractive aspect on these gems. Other samples were orange-yellow and did not change a color underrepparttar 109305 various sources of lighting. Unfortunately,repparttar 109306 very hard and compact rock in this place, did not allow to extract many stones from it, andrepparttar 109307 occurrence was abandoned a few weeks after its discovery.

Opposite, first samples cut in 1996 showing a change of color. Above, an orange malaya found also inrepparttar 109308 primary occurrence. (It does not change a color) This is two years later, exactly in September 1998, that returning inrepparttar 109309 small village,repparttar 109310 samples more or less similar to those which I make cut in 1996 were found. They were turbid because ofrepparttar 109311 fine rain of small bubbles they contained. Their color was definitely more orange than malaya garnets fromrepparttar 109312 first occurrence. Indeed, they did not come fromrepparttar 109313 same place. This is a little more than one kilometer of distance thatrepparttar 109314 elluvionnar deposit was discovered. I was immediately conscious to berepparttar 109315 witness of a rare moment inrepparttar 109316 career of an impassioned person in precious stones.

Madagascar corundums ( Sapphire & Ruby discovery )

Written by Alain Darbellay GGGems


© 2004 gggems.com All rights reserved.

AL2O3 Sapphire found in a metamorphized limestone. · Crystallographic properties of corundum: Trigonal.c = 1,3630 pp 0 86°4' ; pa1 = 122°26' Macle according to p (1011), often polysynthetic, accompanied by plans of separation, similar plans are also observed according to a1 (0001) unequal break to conchoïdal. Hardness 9. Density 3,95 to 4,1 Refractive index: 1.76 - 1.77 Uniaxial and optically négative.ng = 1,7675; Np = 1,7593 The faces a1 frequently showrepparttar phenomenon of asterism, generally due to reflexions within separation p. Strong polychromatism , with following maximum ng. · Chemical properties: corundum is composed of pure alumina; its colouring is due to metallic oxide traces or inclusions. The color of sapphire, due to iron and titanium oxide, gives its best effect under daylight. Electric light makes it often dark. The color ofrepparttar 109296 ruby, due to chromium oxide, onrepparttar 109297 contrary shows its most luminous red under electric lighting. The Corundum shows in Madagascar two different aspects: 1 stony and opaque crystals. 2 crystals of smaller size often transparent and usable as gem. In Madagascar, stony corundum comes from mica schists metamorphized by granite, as well as granitic veinules endomorphized and more or less deprived of quartz which injects those. Silimanite is a usual satellite of corundum in this type of deposit. One also finds some in eruptive rocks, syenites. Gems are generally found in alluvium, but come either from basaltic slags, or from metamorphized limestones or endomorpheous feldspatic rocks. 1 2 3 4 5 One distinguishes two principal types of corundum in Madagascar: Type I : isoceloedric, more or less acute accompanied or not by a small face a1 (0001) and more rarely by facets p (1011). Represented by figures 1 to 11, but which often become complicated in consequence ofrepparttar 109298 irregularity ofrepparttar 109299 development of some of their faces and by stacking with parallel axes of a great number of individuals. 6 7 8 9 10 11 12 13 Scalenoedron Stacking with parallel axes, Crystal supporting on one of its bases gutters at contours ofrepparttar 109300 face. a small rhombohedron p in parallel position. Type 2: Characterized byrepparttar 109301 association ofrepparttar 109302 prism d 1 (1120) at a broad base, with which can associaterepparttar 109303 isosceles ones, among which e 3 is most frequent, as well asrepparttar 109304 rhombohedron p. The base of Malagasy corundum crystals very frequently shows scratches or triangular figures in relief, limited by p. Macle of blue corundum. Translucent violet - pink sapphire

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