Synthetic Green Quartz

(via ICA Early Warning Flash, No. 63, November 17, 1992) GIA GTL writes:

Background
At the Tucson Gem and Mineral shows in February of 1991, we noted dealers offering large quantities of synthetic quartz, reportedly of Russian origin. Among these was a transparent dark green type that visually resembles tourmaline. This green synthetic quartz was also being offered at the Tucson shows this past February; it was our impression that even more faceted material was being offered this year.

Recently, the GIA Gem Trade Laboratory, Inc in Santa Monica received for identification from two separate clients faceted specimens of what we identified as dark green synthetic quartz. In both cases, the material has been represented to our clients as a new type of natural green quartz from Brazil.

Gemological properties
Gemological testing revealed refractive indices, birefringence, and specific gravity consistent with quartz, both natural and synthetic. The specimens were inert to both long and short wave ultraviolet radiation.

Examination under immersion between crossed polaroids shows that the material was untwined, with a bulls eye optical interference figure. Under magnification we noted parallel green color banding similar to that seen in a reference sample of synthetic green quartz of Russian origin. Also noted was some angular brown color zoning that ran perpendicular to the green banding, a feature we have noted in other colors of hydrothermal synthetic quartz. One specimen also contained numerous tiny white pinpoint inclusions of undetermined origin.

Chemistry
Energy Dispersive X-ray fluorescence detected the presence of silicon, potassium, and iron. This differed only slightly from the chemistry of the synthetic green quartz reference specimen. It is believed that the iron detected is responsible for the green coloration.

Discussion
In the above cases, the client’s specimens were all identified as synthetic green quartz. It is important to note that, while green quartz does occur in nature (and is sometimes referred to as praseolite or prasiolita), such material is typically light in tone. To our knowledge, natural green quartz with this depth of color has not been reported.