Turquoise. From Tucson to Tibet to Turkey, this sky-blue stone has fascinated people for at least three thousand years. Turquoise is a phosphate of copper and aluminum, so it is found most often in the U.S. in copper mining areas. Its colors can vary from light aqua to rich sky-blue, then all the way to teals and greens, depending upon mineral content. It is an opaque stone that has a rich history—It was used for jewelry and currency by Native Americans, and also was mined in Iran and found its way through Turkish bazaars all the way into Europe (hence the name, which mistakenly attributed its origin to Turkey). Today’s biggest producers of turquoise are the U.S. and China.
Turquoise is not a tough stone. The best turquoise is only a bit harder than window glass, and the worst is as soft and porous as chalk. As a result, most turquoise is treated in some way. These treatments are not necessarily a bad thing. For example, good medium grades of turquoise are treated primarily to strengthen the stones and accentuate and deepen, but not change, their color. The end effect is equivalent to spraying water on a stone—the color “pops.” In the U.S., this treatment is called stabilization and I’ll discuss it in detail later.
Lower grades of turquoise, which are very soft and crumbly, can be pulverized and mixed with a binder to form reconstituted turquoise. Reconstituted turquoise can be found in cheap souvenir jewelry, and personally I don’t think it’s worth working with. It’s on the same level as base metals. It is easy to pick out reconstituted turquoise because the stone looks like it contains little pieces of aqua confetti. It’s also helpful to know that imitations exist that don’t contain any turquoise at all—they’re either some sort of plastic, or another stone that’s been colored to look like turquoise. I recently came across a website selling “Howlite Turquoise.” There is no such type of turquoise. It’s a soft white mineral with black inclusions called Howlite that has been soaked in dye.
The most valuable type of turquoise is untreated in any way. The term that’s used to distinguish untreated turquoise is “unstabilized.” I’ll get to stabilization in a minute, but for now, it’s important to know that untreated, or “unstabilized” turquoise is the rarest and most valuable. Unstabilized turquoise might have a shiny surface, but this is simply from the compounds used in polishing.
Unstabilized turquoise comes in its natural color, which could be any of the colors discussed above. It can also contain patterns, a mix of colors, and veins of other minerals such as silvery pyrite, black tenorite, or white quartz. It can also have seams, healed fractures, and other natural imperfections. Often natural, unstabilized American turquoise is “backed,” or glued on to a tough plastic (devcon) backing that helps protect it. This does not detract from its value; in fact, it’s good to have a backed stone because that protects it from cracking over time. Native Americans have been backing their turquoise for a while, so that is one clue that the stone is unstabilized.
What I’ve found interesting about unstabilized turquoise is that each mine seems to produce a characteristic color or patterning. If you see turquoise with lots of bold black in it, chances are it’s from the Ajax mine in Nevada. Royston, NV turquoise sports a soft green color, while turquoise from the huge Morenci copper mine in southeastern Arizona is a beautiful deep aqua blue. Birdseye turquoise from Kingman, AZ is very light aqua with a pattern of fine lines that look (to me) like the shadow pattern of water in a swimming pool. Unfortunately, the Kingman mine is now closed, so any Birdseye turquoise is rare.
There does exist a flawless natural turquoise without seams or fractures. Its color is a consistent, intense robin’s egg aqua blue and is considered “gem-quality” turquoise. Iranian, or Persian turquoise was of this high gem quality, but that material is no longer readily available. That’s not a tragedy because there is one other source of this fine material, and that is outside Globe, Arizona. Here, the Sleeping Beauty mine has been producing this rare, and thus very expensive, gemstone. In fact, all turquoise given the name “Sleeping Beauty” must come from that mine.
The majority of turquoise from around the world is stabilized. I asked master lapidarist Keith Horst about this process, because Keith started out his career specializing in turquoise, and if anyone knows about it, he does. He even teaches a special course just on turquoise at Yavapai Community College.
Keith told me that stabilization is a process developed by Leonard Hardy in Kingman, Arizona, nearly fifty years ago. It’s a chemical process where chunks of natural turquoise are immersed in buckets of polymer resin, covered, and left to sit. The polymer resins mix in the same way you would mix the components of epoxy glue, and in mixing, a chemical reaction occurs that generates heat. The heat buildup inside the closed bucket creates a vacuum, which draws the resins into the porous turquoise chunks. So stabilization is not a surface treatment—it penetrates and permeates the stone.
After the appropriate time has passed for the chemical reaction to be completed, the bucket is emptied and the turquoise chunks have to be hacked out of the resin matrix. These chunks are cleaned up, but Keith says that the easiest way to tell whether a piece of turquoise has been stabilized is to look closely at the rough—little translucent nodules and bits of shiny, plastic-like material can usually be seen here and there on the outer surface of the chunk.
Keith says there are two types of stabilizing mixtures. One, called “clear shot,” doesn’t change the color of the turquoise; it just makes it richer and easier to see. The other, used on low-grade turquoise, is called “color shot,” because it adds dye to the stone. The result is what Keith calls “Tidy-Bowl blue,” and to the experienced eye, it looks oversaturated and phony.
Keith sees nothing wrong with clear shot stabilization. He says that most of the peoples who mined turquoise throughout history, treated the stone in some way, primarily to protect and preserve it. “Even the ancient Navajos added sheep fat to turquoise to enrich the colors,’’ he says.
In my personal opinion, the most important part of turquoise is that the material is in its original form (not reconstituted), and that the color is natural. Beyond that, it is up to the designer, and the customer, to decide whether they prefer stabilized or unstabilized cabochons. Purist might insist on only unstabilized stones, but some of the more interesting patterns and colorations are available only in stabilized pieces. So it’s up to you.
The bottom line for both types of top quality turquoise is that it has to be treated with care. Turquoise jewelry should be stored wrapped or bagged to prevent it from being scratched in jewelry boxes by harder stones. It should NEVER be sonic-cleaned, only lightly washed with mild soap and water. Exposure to the sun, perfumes, and oily skin can change the colors, so those should be avoided.
Turquoise is a beautiful gem. It graced the fabulous burial mask of the Egyptian Pharoah Tutankhamun, and was worn by Persian kings as well as by the Anasazi of Chaco Canyon. So if you choose Turquoise, you should know that you are in good company.
By now, you must be asking yourself where you can find a reputable place to see these different types of turquoise and know what you’re buying is what it says it should be. That’s easy—come to my website. I have just posted a variety of beautiful turquoise cabochons on my Heart of Stone Studio website, www.heartofstonestudio.com. So come see and buy the beautiful types of turquoise—both stabilized and unstabilized, all natural color—that I’ve been talking about: Click here.
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