Blue Spinel from Tanzania

Spinel is a gemstone that at one time was most famous for being mistaken for ruby or sapphire. These days spinel gets the respect it deserves -- it is recognized for its excellent hardness (8 on the Mohs scale) and brilliance, and the fact that, unlike most ruby and sapphire, spinel is never heated or treated in any way.

Spinel is now in great demand among gem dealers, who rarely can find enough stock to satisfy their customers. But natural spinel is rarely found in the mass market, since the supply is so limited that most jewelry stores don't carry it.

Spinel is a magnesium aluminate, typically colored by chromium and iron. It forms as a cubic crystal like a diamond. However, unlike diamond, which has perfect cleavage, spinel has very poor cleavage. That makes it easier to cut and a more durable gem for jewelry. Due to spinel's very good dispersion, gem spinels can possess vivid fire, and the intensity of spinel color is in part due to the fact that spinel is one of the few singly refractive gemstones, the others being garnet and diamond.

Greenish Blue Spinel

Red is the most famous color in spinel, but spinel occurs in a range of colors, including pink, violet, orange, silver and blue. The red and pink spinel are the most prized, followed by the lavender and blues. Any spinel over 2 carats is rare, and good stones over 3 carats count as very rare.

Blue spinel is a rather special stone. There are actually very few gems which occur naturally in blue. Blue sapphire is the most famous. But blue topaz is the result of irradiation treatment, and tanzanite must be heated before it turns blue. In the deeper blue colors, there are only softer stones such as kyanite and iolite.

Deep Blue Spinel

The colors of blue spinel range from blue-gray to violet blue to greenish blue and cobalt blue. The lighter tones tend to display more brilliance and fire and display well under different types of light. Some of the darker shades with a gray secondary hue can look less lively under incandescent lighting.

Burma and Sri Lanka are the traditional sources for fine spinel, though the Burmese material is generally recognized as superior. Recently some high quality African spinel has come on the market, with some pieces in good sizes. We have found excellent spinel from Tanzania in red, pink, violet, and blue; and occasionally in unusual colors such as orange and purple. The supply of Burmese spinel is very limited but steady, and the material is generally of very high quality.

First Published: February-24-2009

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