The identification of Zachery-treated turquoise

Abstract

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 effi-ciently, by EDXRF spectroscopy - as it contains significantly more potassium than its untreated counterpart. © 1999 Gemological Institute of America.