Natural turquoise — hard enough to grind and polish without any treatment — represents roughly 15 percent of total world production. The other 85 percent is too soft to cut for jewelry without intervention. Every treatment, from surface waxing to stabilizing and the Zachery process, is documented here, along with the manufactured materials, block and reconstituted, that are a separate group.
The hardness problem drives the entire treatment industry. "An average of 85 percent of the total mining production of turquoise yields turquoise that is too soft…" (Lowry, Turquoise: The World Story.) Chambless frames the same fact from the other end: "Turquoise is relatively soft, and it is estimated that at least 80 percent of it is too soft to cut successfully for jewelry without having the stone cracking, losing luster, or changing color." (p. 175.) Both sources agree: gem-grade natural turquoise is the exception, not the rule. As Chambless puts it, "Natural (untreated) high-grade turquoise is among the rarest of all gemstones, certainly far above diamonds, and gem-grade is the rarest of the rare." (p. 175.)
The stabilization industry has a specific origin story. Lowry documents it in some detail: "In the United States during the 1950s and 1960s, on the sunporch of an unknown old man's home, which was located on a hillside above Globe, Arizona, Leonard Hardy and several others were introduced to 'soak treating' turquoise." (p. 197.) The original electrochemical method was blunt: "place 'chalk' turquoise in a large stainless steel pan with electrodes placed at each end. Next, they added petrochemicals and blue dye along with the chalk and then generated volts of electricity to impregnate the turquoise and the chemicals together." (p. 198.) The result is firmer stone — but Lowry is unambiguous: "Stabilized turquoise is not natural turquoise."
The most sophisticated modern treatment is the Zachery process, developed by Jimmy Zachery. Lowry describes it: "Jimmy's science and turquoise background combined to develop beautiful-looking turquoise. This patented process can be used to treat either cut cabochons or rough turquoise." (p. 203.) In our terms, Zachery-treated turquoise is enhanced (hardened).
Stabilizing itself comes in two kinds, which Lowry names on the same page: a "clear shot" with no added dye, and a "color shot" with dye. Even clear shot changes the color you see. Lowry: "The index of refraction is changed and thereby the color perceived. You will find that clear shot stabilized turquoise is not the same color as the chalk." (p. 203.) In our terms, clear shot is stabilized, and color shot is stabilized enhanced.
Kitchen and surface treatments predate the industrial era. Applying Crisco, mineral oil, or wax to soft turquoise is the oldest enhancement method — documented by Lowry — and entirely temporary: the surface enhancement fades with wear and heat.
At the far end of the spectrum, the Gilson synthetic emerged in the 1970s. Lowry: "In the 1970s, he [Pierre Gilson] developed a synthetic turquoise that was said to be mineralogically identical in every way to natural turquoise. This process produced an imitation to the clarity and robin's-egg blue color of Persian turquoise." A black matrix version was subsequently added. Gilson synthetic is not mined turquoise of any grade — it is a laboratory creation.
Bedinger also records that altered and imitation turquoise entered the market as early as the railroad era — the practice of treating stone is far older than modern stabilization.
See the Silversmith Directory for artists who source and disclose material treatments. See also Turquoise Imitations and Fakes for materials that are not turquoise at all.