Turquoise, the robin's egg blue gemstone worn by Pharaohs and Aztec Kings, is probably one of the oldest gemstones known. Yet, only its prized blue color, a color so distinctive that its name is used to describe any color that resembles it, results in its being used as a gemstone. Turquoise has been, since about 200 B.C., extensively used by both southwestern U.S. Native Americans and by many of the Indian tribes in Mexico. The Native American Jewelry or "Indian style" jewelry with turquoise mounted in or with silver is relatively new. Some believe this style of Jewelry was unknown prior to about 1880, when a white trader persuaded a Navajo craftsman to make turquoise and silver jewelry using coin silver. Prior to this time, the Native Americans had made solid turquoise beads, carvings, and inlaid mosaics. Recently, turquoise has found wide acceptance among people of all walks of life and from many different ethnic groups.
The name turquoise may have come from the word Turquie, French for Turkey, because of the early belief that the mineral came from that country (the turquoise most likely came from Alimersai Mountain in Persia (now Iran) or the Sinai Peninsula in Egypt, two of the world's oldest known turquoise mining areas.) Another possibility could be the name came from the French description of the gemstone, "pierre turquin" meaning dark blue stone.
Chemically, a hydrated phosphate of copper and aluminum, turquoise is formed by the percolation of meteoric or groundwater through aluminous rock in the presence of copper. For this reason, it is often associated with copper deposits as a secondary mineral, most often in copper deposits in arid, semiarid, or desert environments.
For thousands of years the finest intense blue turquoise in the world was found in Persia, and the term "Persian Turquoise" became synonymous with the finest quality. This changed during the late 1800's and early 1900's when modern miners discovered or rediscovered significant deposits of high-quality turquoise in the western and southwestern United States. Material from many of these deposits was just as fine as the finest "Persian." Today, the term "Persian Turquoise" is more often a definition of quality than a statement of origin, and the majority of the world's finest-quality turquoise comes from the United States, the largest producer of turquoise.
The increased acceptance of turquoise resulted in higher prices, some of the most desirable materials going for as much as $2,200 per kg. The increased demand could not be met through production of acceptable mine run materials. Therefore, an industry emerged--the business of turquoise stabilization, reconstitution, and the manufacture of synthetic and simulated turquoise. In most instances, the stabilization and reconstitution of turquoise involve the use of earthy or highly porous types of turquoise which are pressure-impregnated with hot acrylic resins. The resins improve the color, hardness, and durability of the material to a point that inexpensive porous, poorly colored, or nearly colorless materials become suitable for use in jewelry. As long as the materials are represented as treated, stabilized, or reconstituted, the marketplace can accept or reject the materials based on decisions that are purely business or economic.
(The above was copied from http://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/turquoise.html on 1/4/2009)
The Turquoise Market in New Mexico and Arizona
Most Zuni and Navajo artists purchase turquoise from trading posts and itinerant mineral dealers. The carvers and silversmiths prefer the "treated" forms of turquoise, both because they are easier to carve without chipping, cracking, or breaking and because the price is lower. No documentation is provided to the artists. Upwards of 90% of the turquoise used by the Indians is "treated" - and it is customary in the trade to assume this without further discussion when selling American Indian art items containing turquoise.
There are so many forms of "treatment", from resin soaking to space age chemistry, that is not possible to reliably distinguish treated from untreated turquoise by the naked eye. Chemical tests are not routinely available, and even these might not distinguish some modern forms of treated turquoise from natural.
Here is a story told by many traders - the numbers vary from mine to mine. Arizona and Nevada copper mines are famous for producing turquoise... The owners of some of the copper mines have contracts to dump anything with turquoise veining or nuggets into trucks for treatment. About 95% of this is sent away for treatement, which makes it very affordable. Of that stabilized stone, 50% is then shipped to China for cutting; the other half is sold in the rough to American artists and those in the turquoise trade. The remaining 5% of the turquoise-bearing rock stays in its natural state.
In order to know that turquoise is in its natural state, one must be able to track the turquoise from the mine to the customer. You must have proof that the turquoise was not treated by any trader who handled it at any stage in the process. In today's market, without documentation at every step in this process, it is essentially impossible to prove that any turquoise is untreated.
Sunshine Studio recommends that you assume that all turquoise in today's American Indian market has been treated in some way unless clear documentation to the contrary is provided. This includes all turquoise on our web site, both antique and contemporary.
Sterling Silver, Turquoise, Malachite, Gold-Lip and Jet Bird, Parrot by Stephan Lonjose - Zuni Jewelry