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Certified Natural Black Spinal AAA Quality 5 mm Faceted Round Shape 25 pcs Lot Loose Gemstone
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Quantity:25 pcs Lot
Stone:Natural black Spinal
Hardness:8
Type:Certified Natural Stone
Shape:Round
Size:5 mm
Clarity:Opaque
Black Spinel is extremely rare and in most cases rarer than Rubies. Black spinel is not well-known among the gem world, yet its outstanding features make it the ideal choice for an opaque black gem.
Black Spinel is believed to protect its owner from harm, to reconcile differences, and to console sadness.
Some say that black spinel is the stone for people born on Saturday and it is the recommended gift for the 22nd wedding anniversary. Black is the essence of style and sophistication with a timeless quality that means it will never go out of fashion.
Hardness of Black Spinel is 8
Spinel Treatments:-
Weigel (1923) gives early references on the heat treatment of spinel and reports that purple and pink spinels change to yellow above 1000°C, but may revert on cooling; blue spinel changes to green at 900°C and to yellow above 1200°C and this color change does not revert. Red spinels were reported to have had their color improved by a heat treatment which removes a brownish components and leaves a pure red (R. Crowningshield, unpublished information).
Synthetic spinel (Nassau, 1980) is usually grown by the Verneuil technique with an excess of Al2O3 to make growth easier. At the large excess composition, MgO · 5Al2O3, the resulting clear product is unstable and fine crystallites of alumina precipitate on annealing. This forms a strong schiller, yielding a fine moonstone imitation (Nassau, 1980; Breebart, 1958). The refractive index of 1.73 is quite different from the 1.53 of moonstone, as is the specific gravity of 3.64 to 3.66 compared to 2.57.
Significant Gem Localities:-
Black Spinel can be found in Myanmar, Sri Lanka, Tanzania, Afghanistan, Cambodia, China, Pakistan, Russia, Tajikistan, USA, Vietnam, Kenya, Madagascar and part of the former Soviet Union Tajikistan.
Quantity:25 pcs Lot
Stone:Natural black Spinal
Hardness:8
Type:Certified Natural Stone
Shape:Round
Size:5 mm
Clarity:Opaque
Black Spinel is extremely rare and in most cases rarer than Rubies. Black spinel is not well-known among the gem world, yet its outstanding features make it the ideal choice for an opaque black gem.
Black Spinel is believed to protect its owner from harm, to reconcile differences, and to console sadness.
Some say that black spinel is the stone for people born on Saturday and it is the recommended gift for the 22nd wedding anniversary. Black is the essence of style and sophistication with a timeless quality that means it will never go out of fashion.
Hardness of Black Spinel is 8
Spinel Treatments:-
Weigel (1923) gives early references on the heat treatment of spinel and reports that purple and pink spinels change to yellow above 1000°C, but may revert on cooling; blue spinel changes to green at 900°C and to yellow above 1200°C and this color change does not revert. Red spinels were reported to have had their color improved by a heat treatment which removes a brownish components and leaves a pure red (R. Crowningshield, unpublished information).
Synthetic spinel (Nassau, 1980) is usually grown by the Verneuil technique with an excess of Al2O3 to make growth easier. At the large excess composition, MgO · 5Al2O3, the resulting clear product is unstable and fine crystallites of alumina precipitate on annealing. This forms a strong schiller, yielding a fine moonstone imitation (Nassau, 1980; Breebart, 1958). The refractive index of 1.73 is quite different from the 1.53 of moonstone, as is the specific gravity of 3.64 to 3.66 compared to 2.57.
Significant Gem Localities:-
Black Spinel can be found in Myanmar, Sri Lanka, Tanzania, Afghanistan, Cambodia, China, Pakistan, Russia, Tajikistan, USA, Vietnam, Kenya, Madagascar and part of the former Soviet Union Tajikistan.
