In current usage, “natural turquoise” is used in two ways. First, the phrase is used to describe turquoise that has not been treated in any way with dyes, stabilizing epoxies, or other chemical treatments intended to alter the color, hardness or luster of the stone. Natural turquoise cannot be easily found in the marketplace. The purist who seeks it is advised to buy direct from the mine. It has been claimed that as little as 3-10 percent of turquoise mined is of sufficient hardness to be used in jewelry without stabilization. Natural turquoise is rare, indeed.
The term has also been used to describe turquoise that has not been treated with dyes or epoxies, but has been given a wax or oil coating for protection. Since the porosity of turquoise can lead to discoloring, staining and dehydration, only the most conservative purist would object to wax coatings.
"Natural Processed Turquoise"
“Natural processed” seems like an oxymoron to us, but the phrase is now starting to appear in the marketplace. This is a proprietary method, so we know very little about it. Apparently, turquoise is soaked in nontoxic chemicals to increase luster and color. The method is also claimed to leave no physical evidence of alteration. One advantage is that turquoise subjected to this secret treatment is less likely to turn green over time.