Turquoise stands the test of time
Turquoise is a natural stone that has been mined for jewels for thousands of years. Most notable were the Egyptians who established the first mines in the Sinai. Other areas of the world also found beauty in the blue-green stone. Evidence of ancient mines exists in the Americas, Middle East and in Asia.
The color of turquoise can range from deep blue to a deep green with lots of variation between the two. The more copper a stone has the bluer it will appear, and the iron content will determine how green it appears. Often one will note veining throughout the stone.
Mining turquoise since ancient days means that the reserves we have available today are limited. For that reason distributors have gotten creative in what is sold to the public as turquoise jewelry. There seems to be several levels of quality in turquoise stones.
The highest level is the natural stone that comes right from the mine and is made into jewelry. Other than cutting and polishing almost gem level stones have very little enhancement. The next level down would be imperfect stones with no luster. These stones are still of value but a buyer needs to understand they have been changed from their natural state. The stones have been submerged into a stabilizing compound that hardens and fills the porous stone. Color can and is adjusted in this process.
Reconstituted turquoise is another level that is made up of bits and pieces of turquoise that otherwise are unusable. These pieces are ground down to a powder, additives are mixed with the powder, and voila, turquoise bricks, beads and more are produced. Jewelry made from this process will probably have very little turquoise content. Finally, there is the jewelry made from colored resin that has no turquoise content but can look pretty good.
How is a person to know what they are buying? Written documentation is the best recommendation because all of these processes are pretty sophisticated, and the levels are hard to decipher. Other good sources of information for the consumer prior to purchase are located on eBay and eHow.
All turquoise is soft and porous, hence the use of enhancements. However, if you want to get the real thing you might consider an antique piece. It's a pretty sure bet that most of these processes were not in effect a hundred years ago.
Jean McClelland writes about antiques for The Herald-Dispatch.