Turquoise
Turquoise, with its remarkably distinctive greenish-blue color, has been employed for ornamentation by many ancient cultures throughout the ages.  Today it is still in use due to the same appeal it held in the past as its sole claim to beauty—its color.  The name “Turquoise” is derived from the French term, turquie, or “Turkey Stone,” referring to the material that was imported into Western Europe from Turkey.  Turquoise once travelled an ancient trade route from its origins in Iran and possibly the Sinai Peninsula, from which it was delivered to Turkey to be traded in Europe.  Although the deposits in the Sinai Peninsula are now depleted, Iran continues to be a major producer of high quality Turquoise to the present day.  Other producers of Turquoise include China, Afghanistan, Argentina, Australia, Brazil, Israel, Mexico, Tanzania and the United States (specifically, California, Arizona, New Mexico and Nevada).
 
The best quality of Turquoise comes from deposits near Nishapur in Iran (Persia).  This Turquoise tends to be of an even slightly greenish-blue color with no veining or limonite matrix present.  The best quality is semi-translucent rather than opaque, and is somewhat waxy in appearance due to its low porosity.  Turquoise with brown, dark gray or black veins or matrix (host rock), termed “Spider Web Turquoise,” is equally as popular.  “Sleeping Beauty Turquoise” refers to the high-quality Turquoise that is extracted from the Sleeping Beauty mine in Arizona; it can rival the best Turquoise from Iran.     
 
Turquoise can be quite porous and, as a result, can be discolored by skin oil, perspiration or other oils, such as perfume or soap, with which it may come into contact.  Therefore, it is advised to remove Turquoise rings before washing hands.  Due to the porous nature of Turquoise, small chips and the dust and residue of cutting Turquoise can be compressed and bonded with a plastic or resin to form reconstructed Turquoise, a much cheaper imitation of natural Turquoise that possesses deeper color and is harder in texture.   Synthetic Turquoise, originally created by Pierre Gilson, can be readily identified by using magnification and then viewing the spectrum of the stone in question.        
 
Turquoise Properties
Species:  Turquoise
Trade Terms:  Persian, Spider Web, Matrix
Chemical Composition:  CuAl6 (PO4) 4(OH)8 5H20
Color: Greenish-Blue, Bluish-Green
Hardness:  5 to 6
Crystal System:  Triclinic
Refractive Index:  1.610 - 1.650
Specific Gravity:  2.76 (+.14, -.36)

Image by Andreoli.
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