Thursday, July 21, 2011

Turquoise By So Many Names

Turquoise By So Many Names

Do you ever wonder what the difference is between genuine Turquoise, Chalk Turquoise, Stabilized Turquoise, Turquoise Magnesite, Turquoise Dyed Howlite? It's really hard to tell with the naked eye these days. All I know is I love the color and it's my birthstone (December). So did a little reading on it. Here's a bit of info to get you in the know.

Turquoise is a blue-green mineral, a copper aluminum phosphate, valued for its rarity and unique hue, and widely used as an ornamental stone.
This stone is fragile, just slightly stronger than window glass, so special care must be taken during extraction and transport.

The bluer the stone is, the more expensive. Variations in color are due to the presence of metals, such as iron impurities in the case of green turquoise. Genuine turquoise is expensive there fore imitation and artificial turquoise is available

Chalk Turquoise
Chalk turquoise is a form of natural turquoise that has a white chalk-like consistency. It has the same chemical composition as turquoise, only without the copper (it's the copper that causes the turquoise color). The chalk is then dyed and stabilized to produce a material that's hard enough to use in jewelry with a pleasing turquoise color.
Chalk turquoise is a low-quality variety, found deeper in the soil. As a result, it is much softer and more brittle. On the Mohs hardness scale, chalk turquoise ranges between 2-4, lower than the 6 of higher grades. It lacks the blue shade that defines the mineral. Instead, chalk turquoise is pale blue or white. It may or may not have significant matrixing, the brown or black flecks often associated with Native jewelry of the southwest. "Simulated" turquoise is often touted as being chalk turquoise, when in fact it is just dyed Magnesite or another white stone that absorbs dye easily.

Stabilized Turquoise
Stabilized turquoise costs less than natural turquoise, but is still considered beautiful and desirable. Stabilized turquoise differs greatly from reconsituted turquoise. Reconstituted turquoise is the cheapest type of turquoise.

Stabilized turquoise is created by adding a clear resin to chalk, or soft, turquoise to help enhance the color and well as increase the hardness of the stone. Chalk, or soft, turquoise is usually a lower grade of turquoise as it is too soft to be used on its own for jewelry and must be stabilized with resin. Since turquoise is a very porous substance, the resin fills in the tiny holes and crevices to form a firm stabilized turquoise stone.

Imitations Magnesite Dyed Howlite
The most common imitation of turquoise encountered today is dyed howlite and magnesite, both white in their natural states, and the former also having natural (and convincing) black veining similar to that of turquoise. Dyed chalcedony, jasper, and marble is less common, and much less convincing. Other natural materials occasionally confused with or used in lieu of turquoise include: variscite and faustite;[10] chrysocolla (especially when impregnating quartz); lazulite; smithsonite; hemimorphite; wardite; and a fossil bone or tooth called odontolite or "bone turquoise", coloured blue naturally by the mineral vivianite. While rarely encountered today, odontolite was once mined in large quantities—specifically for its use as a substitute for turquoise—in southern France.


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