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Stabilized turquoise - Turquoise that is soft or normally referred to as "chalk" Turquoise is infused with a clear epoxy resin. This resin, under pressure, is absorbed into the rock, which permanently hardens the rock and deepens the color. Unlike the collectible natural tTrquoise which deepens in color over time by gradually absorbing oils from the skin as it is worn, the colors in stabilized Turquoise are permanent. Most of the Turquoise on the market today is stabilized and should not cost as much as natural Turquoise. Stabilized turquoise can be very beautiful, and is a good buy. Because of it's hardness and consistant color, stabilized Turquoise wears much better in Jewelry.
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Black Agate (Onyx) which is truely a died black Agate, is more common and perhaps the most famous variety, but not as common as natural Onyx. Onyx is a crypyocrystalline form of Quartz. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Specimens of Onyx contain bands of colors of white, tan, and brown. As stated, the pure black form which most people know as Onyx, is not a naturally occuring variety. Black Agate or poorly colored Onyx is heated and dyed black to come up with the pure black form so well liked within the jewelry industry.
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