Gemstone Review – Green Amethyst
From time to time we get an email asking us whether we sell something called green amethyst. Since amethyst, by definition, is the violet to purple shade of quartz, there is really no such thing as green amethyst. The term “green amethyst” makes as much sense as “red emerald” or “yellow ruby”. Some gemstone varieties are simply defined by their distinctive color.
Having said that, clearly the customer is in search of something that someone has described as ‘green amethyst’. What is it? Where does it come from? Does it have anything to do with amethyst?
What the customer is looking for is something known by gemologists as prasiolite. The name comes from the Greek for “leek-green”. Prasiolite is a golden-green quartz, somewhat similar in color to peridot or gold-green beryl.
|Synthetic Green Quartz|
This type of green quartz does not occur naturally. It is produced by heating amethystor yellowish quartz. However, not all amethyst or yellow quartz can be heated to produce prasiolite. According to gemological sources, only quartz from the Montezuma deposit in Minas Gerais, Brazil, can be heated to produce prasiolite. Amethyst or yellowish quartz is heated to about 500 degrees centigrade to produce the leek-green color. Unfortunately, the color is known to fade when exposed to strong sunlight.
Some so-called ‘green amethyst’ on the market is actually synthetic quartzproduced by the hydrothermal method. It is usually found in a vivid mint-green or blue-green rather than the paler golden-green of prasiolite. The unnatural color is usually a sure sign that it is synthetic.
There are some other varieties of green quartz that occur naturally. These are members of the chalcedony quartz family. They include chrysoprase and aventurine. Aventurine is mainly dark-green, sometimes with a glittery metallic appearance caused by included green mica. Chrysoprase is colored by trace amounts of nickel. Its color varies from apple-green to deep-green. Both are completely natural gemstones.
Finally, we haven’t yet answered the question of why prasiolite is being sold as “green amethyst”. Sadly, the answer is simple greed. Since amethyst is the most valuable gem in the quartz family, associating this green heated quartz with the nobler amethyst is just an attempt to elevate the humble prasiolite. There are certainly many finer green gems on the market, with much better color stability.