Most of the turquoise on the market has been treated in some way to deal with two problems intrinsic with this gemstone. First, turquoise is soft, sometimes even brittle, and thus susceptible to facture. Second, turquoise is porous. As a result, it is susceptible to staining, discoloration and fading. These two problems can be addressed in several ways, but most commonly are managed by stabilizing the turquoise (discussed below).
Another problem is that quality turquoise is getting harder to find. Many mines have been depleted and are now closed. The turquoise coming out of other mines is of lower quality than was once produced. As a result, methods have been developed to create turquoise with the appearance of quality by dying pale shades and by creating stones out of "chalk turquoise" (called reconstituted turquoise).
It should be noted that turquoise has been treated for thousands of years, usually with waxes and oils. Modern techniques represent "advances" on old solutions. Furthermore, many of the various types of gemstones sold these days have been treated in some way to harden them and create clearer crystals; heat treating is especially common.
Zachery Enhancement Method
There is another method that is often used called the Zachery Method. The method is named after its developer, James E. Zachery, an electrical engineer and active trader of turquoise.
This is a proprietary enhancement method, the specifics of which are not public. The method can only be used on turquoise that is of moderate quality. The turquoise is soaked in a non-toxic, secret chemical brew. When dried, the stone is easier to polish and the colors may be slightly more vivid. The only way to determine if a stone has been treated with this method is by destroying it and subjecting it to a chemical analysis. In a study by Fritsch et al., published in Gems and Gemology, it is reported that turquoise that has been treated with the Zachery method has more potassium than natural turquoise. What other chemicals might be used in the process is unknown.
This method is regarded highly by many in the trade because it is largely undetectable, even through the eyes of an expert; leads to a stone with greater luster; and does not involve the use of dyes and hardening agents. However, since it does not strengthen the stone in any substantial way, its use is restricted to good quality turquoise.
Virtually all turquoise on the market has been treated with a clear epoxy, resin or some other form of liquid plastic. A simple approach is to soak turquoise rough (the raw stone) for a long period of time in a hardening solution. Newer approaches involve "pressurized impregnation," in which pressure is used to force the hardening solution deep into the turquoise rough.
After drying, the stone can be cut, formed into cabochons or other shapes, polished and sold. The final product will look like a shinier and smoother version of natural turquoise. It will keep its color and be more resistant to scratches and dirt.
Stabilization is clearly much further removed from nature than simple waxing and oiling. It does have an advantage, however. Stabilization not only protects the stone from dirt, but also reduces the chances of fracturing. Second, waxing and oiling do not solve the problem of "bloom," in which materials from within the stone leak out over time to create an outer white deposit.
Our position on stabilization is simple: Given the nature of turquoise, together with the growing shortage of gemstone quality turquoise, stabilization is often necessary. We object only when the consumer is not informed that the turquoise they are buying has been treated in this fashion.
Much of the stabilized turquoise has also been color-treated. Dyes have been used to bring a stone closer to the Persian Blue that we all value. Another strategy is to dye the matrix a darker color to enhance contrast. Stabilization and dying is often accomplished simultaneously by adding a dye to the clear epoxy or resin used to harden the stone.
While we would never buy color-treated turquoise, we have no objection to it provided that the consumer is told what they are purchasing. Much dyed turquoise is sold fraudulently as the real thing, sadly.
Taking yet another huge step away from natural turquoise, we find reconstituted Turquoise. Other sites refer to this as "stove-top" turquoise. We are not sure who the clever person is who coined this phrase, but it is quite appropriate.
With this method, turquoise stones too small to be used for cabochons, beads or freeform nuggets are powered. This powered "turquoise trash," as we like to refer to it, is then mixed with a binding agent, poured into a mold, and then dried. This reconstituted turquoise is then cut into slabs and then used as natural turquoise slabs might be used in jewelry production.
Reconstituted turquoise is quite inexpensive and thus might be suitable for use in low-priced jewelry. We personally object to the idea of reconstituted turquoise; more objectionable is the selling of reconstituted turquoise as the real thing.
There is an imitation turquoise called "block turquoise" that contains no turquoise stone whatsoever. We mention it here because it is often sold as "reconstituted turquoise." The difference is important: reconstituted turquoise contains turquoise power; block turquoise is completely synthetic.
Often Mother Nature creates stunning, high quality turquoise in thin veins that are too slight for stand alone use. These slender pieces of turquoise are thus glued to a base consisting of stone or another material for added strength, then cut, shaped and polished. Sometimes a thin vein of turquoise can be cut with its host stone serving as the supportive base. We like the idea of taking full advantage of what Mom Nature has provided, as long as the consumer knows that the hidden base in his or her jewelry is not turquoise.