History
Turquoise is one of the world’s most ancient gems. Archaeological excavations revealed that Egyptian royalty wore turquoise jewelry as early as 5500 BC, and Chinese artisans were carving it more than 3,000 years ago. Turquoise is the national gem of Tibet, and has long been considered a stone that guarantees health, good fortune, and protection from evil. Turquoise was a ceremonial gem and a medium of exchange for Native American tribes in the southwestern US. They also used it in their jewelry and amulets. The Apaches believed that turquoise attached to a bow or firearm increased a hunter’s or warrior’s accuracy.
The gem’s name comes from the French expression pierre tourques, or “Turkish stone.” The name, which originated in the thirteenth century, reflects the fact that the material probably first arrived in Europe from Turkish sources.
Color
Turquoise can be translucent to opaque, with a color that usually ranges from light to medium blue or greenish blue. It’s often mottled, and sometimes has dark splotches. It might also have veins of matrix running through it. In the material known as spiderweb turquoise, fine seams of matrix form attractive web-like patterns. The most valuable turquoise is an even medium blue, with no matrix, and the ability to take a good polish.
Geography and formation
Turquoise is found in only a few places on earth: dry and barren regions where acidic, copper-rich groundwater seeps downward and reacts with minerals that contain phosphorus and aluminum. The result of this sedimentary process is a porous, semi translucent to opaque compound of hydrated copper and aluminum phosphate. The traditional source for the top color, sometimes described as robin’s egg blue or sky blue, is the Nishapur district of Iran, the country formerly known as Persia. So, quite often, you’ll hear people in the trade call turquoise of this beautiful color “Persian blue,” whether or not it was actually mined in Iran.
Although Persian blue is favored, the turquoise market also places high value on other shades of blue. As with Persian blue, these shades are often associated with a traditional source. For example, American or Mexican turquoise is light blue, or greenish blue to bluish green, while Egyptian turquoise is greenish blue to yellowish green. Scientists believe that the reason some turquoise looks greenish blue is because it contains more iron than pure blue turquoise. The bluer shades are caused by greater amounts of copper. Any greenish color tends to lower the value.
Care and cleaning
Turquoise hardness is 5 to 6 on Mohs scale and the toughness is generally fair to good. High heat and some chemicals can cause discoloration and surface damage. Can be also discolored by cosmetics, and even skin oils or perspiration. Never clean your turquoise jewelry with the ultrasonic and steam cleaning machines. Warm soapy water is one of the ways to clean your turquoise jewelry. Microfiber cleaning clothes also can clean any jewelry without damaging the gems or metal. It’s always a good idea to take your turquoise jewelry off before swimming, taking a shower, and sports activities.
Source: Gemological Institute of America
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