Feature
Gems & Gemology, Spring 1999, Volume 35, No. 1
The Identification of Zachery-Treated Turquoise
Emmanuel Fritsch, Shane F. McClure, Mikhail Ostrooumov, Yves Andres, Thomas Moses, John I. Koivula, and Robert C. Kammerling
Over the last 10 years, millions of carats of turquoise have been enhanced by a proprietary process called the Zachery treatment. Tests show that this process effectively improves a stone’s ability to take a good polish and may or may not improve a stone’s color. It also decreases the material’s porosity, limiting its tendency to absorb discoloring agents such as skin oils. Examination of numerous samples known to be treated by this process revealed that Zachery-treated turquoise has gemological properties that are similar to those of untreated natural turquoise, and that the treatment does not involve impregnation with a polymer. Most Zachery-treated turquoise can be identified only through chemical analysis—most efficiently, by EDXRF spectroscopy—as it contains significantly more potassium than its untreated counterpart.
