Thursday, February 09, 2006

Prasiolite / Green Amethyst

I love gemstones and their history and origins are often equally fascinating. I try to educate myself as much as possible on the materials I use - for some very practical reasons - some stones are too fragile for certain applications, some are not what their names imply. Very few semi-precious stones today are truly "natural" - generally if something can be enhanced, it will be. Enhancement is as old as the use of gemstones - carnelian has been treated for thousands of years to make it's juicy orange-red brighter and more uniform. Many enhancements do not radically alter the stone's aesthetic properties, but make it more durable for use as an adornment - stabilization of turquoise is a good example of this. Some color enhancements are permanent - like heat, irradiation, or high quality dye processes while others are cheap, hastily applied surface dyes that readily wash off. (Needless to say, I make every effort to avoid the latter!) In my continually growing materials index, I have endeavored to compile the results of my research in order to educate interested customers on what goes into their jewelry and how best to care for it. I will also blog about new entries as they come up. Today's topic is green amethyst, also known as prasiolite. Rarely occuring in nature, it is the product of heat treating a certain form of purple amethyst from a particular mine in Brazil (some sources indicate that a suitable form has recently been found in the US, as well.) It is therefore a form of quartz, and consequently quite durable and amenable to faceting. As with all mineral families that change color with heat treatment, prolonged exposure of the finished piece to high temperatures or intense sunlight is not recommended, as undesirable color change could occur. The earrings above feature exceptionally nicely faceted marquis cut briolettes.

No comments: