Madagascar GarnetsWritten by Alain Darbellay GGGems
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right left Deltoid dodecahedron Pentagonal tetraedrical dodecahedron . Almandine in matrix Spessartite (Ambohimarangitra) Malaya (Andoharano) Malaya (Madagascar) Rhodolite (Ankilytokana) Hessonite (Soakibany) Imperial Malaya (Madagascar) In Madagascar, one finds rhodolite in a gneiss rich in biotite, in which (almandite-pyrope) is presented in form of small grains, or with state of large porphyroblasts, generally deprived of geometrical contours, plagioclase (oligoclase with andesine) is feldspar dominating and sometimes exclusive. These gneisses contain sometimes pegmatic beds very rich in crystals. One very finds also garnetiferous gneisses containing little biotite, hardly directed. Kinzigites. The gneisses which have been just enumerated have a very clear schisteous structure, which had with biotite abundance. A rather frequent type is approximately blocks and presents a compact aspect, thanks to prevalence of large garnets without geometrical form, associated quartz and feldspar granoblastic, biotite is not very abundant. The structure points out that of corneal micaceous of contact of granite. This gneiss can be compared with kinzigite of Black Forest. Leptynites with amphibolo-pyroxenite intercalation rich in garnets of a pale pink (almandite-pyrope), with often rutile and graphite abound in certain areas of Madagascar. The feldspar is orthoclase, associated with ogigoclase-albite feldspar and sometimes with spindle-shaped microperthite, there exists much of myrmekite. These rocks are with fine grins, but they very often contain large regularly distributed crystals. Usually garnet does not have a geometrical form, but it takes clear faces in more quartzose zones. Leptynites derive from granites by disappearance of mica; garnetiferous mica schists constitute opposed pole in which biotite prevails, with progressive disappearance of feldspar. The Besafotra river carry out spessartites on several kilometers from their source, doubtless a sodolitic pegmatite. A walk of 25 kilometers among mountains is necessary to reach this place. SPESSARTITE GARNET The tanety "grounds bordering river," are also object of orange garnet's fever. Sifting in river. Initially, spessartite appeared in Besafotra river, searched out here near to its source. Ankilytokana, one of fabulous rhodolite occurrences exploited in a leptynite vein on a sixteen meters depth. RHODOLITE GARNET Leptynites are primarily consisted in alkaline feldspars and quartz. When these rocks are not ribboned, and that is frequent, it is often difficult to decide if a sample, not seen in place, belongs to a leptynite or an aplite, it should be noticed that in Madagascar, these last contain microcline and not of orthoclase. In this area, one observes graphite spangles in leptynites. Malaya garnet discovered into September 1998, in eluvium in a broken up leptynite. The modest depth of deposit did not require a significant work to extract it. This stone shows an exceptional capacity to restore light, thanks in particular to its high refractive index, especially under not very enlightened condition. Malaya Garnet Discovery Cutting Styles¦Characteristics¦ Crystalline Systems ¦ Madagascar Sapphire ¦ Corundum data ¦ Malaya Garnet ¦ Rhodolite Garnet ¦ Spessartite Garnet ¦ Hessonite Garnet ¦
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Madagascar gem safariWritten by Alain Darbellay GGGems
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The far-south of Madagascar, semi-desert, does not present Polychromatic sapphires from Iankaroka discovered in 1990. any asphalt road yet, dust and trepidations are daily lot of any traveller. Sunsets and natural life of its inhabitants offer an appreciable compensation. Rubies from Ianavoha. (South of Madagascar.) Ruby from Andranomilitsy (Vohitany) Syenitic-nephelinic vein of rubies in Andranomilitsy. -------------------------------------------------- In Soamiakatra, rubies were sold with sunglasses. The Mayor of Soamiakatra in 1989, (East of Antsirabe.)
Rubies from Soamiakatra in high plateaus.
Here, rubies are always found in alluvium.
MADAGASCAN CORUNDUMS ----------------------------------------------- BLUE SAPPHIRE NATURAL COLOR Sapphire from Analafady ( Ambondromifehy ) North. The alluvial deposit of Ambondromifehy is exploited since 1996. It is located in a Jurassic limestone, but origin of sapphires is in alkaline basalts from close volcanic zone. Mahatsara ( Ambondromifehy) GGGEMS.COM
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