About a month ago, a client contacted me with a special project for his wife. He wanted to make a custom pendant for her using a gemstone that was both unusual and suited her as a geologist. After some discussion, we settled on green zircon.
Zircon is both a visually interesting gemstone and an important mineral in geology. Some zircons contain very minute inclusions of uranium, thorium and other radioactive minerals. The amount of radiation coming from these inclusions is so small that it is not generally detectable above everyday background radiation; there is no hazard in wearing zircons. But specialized, ultra-sensitive laboratory equipment can measure how much radioactive mineral is remaining in an inclusion. With these measurements and the knowledge that uranium decays at a known rate, geologists can calculate the age of the zircon (and thus the host rock) from the amount of uranium remaining within the inclusion.
Radiation affects the zircon’s crystal structure over millions of years. Eventually, the crystal structure of a zircon goes from well-ordered to amorphous Thus, there are two types of zircon, sometimes called “high zircon” and “low zircon”. More properly, they should be called simply “zircon” and “metamict zircon”. Most green zircons are metamict zircons.
Now, because “radioactive” is an understandably scary word, it’s worth repeating here: there is not enough radiation coming from these stones to above background radiation to affect someone wearing the stone as a jewel… unless you plan on wearing it for millions of years! (If you’re interested in reading more, I’ve provided a couple of links at the bottom of this post.)
My challenge for this project was to find a sizable green zircon in a triangular shape that was suitable for recutting into a pendant stone. Green zircons are not common; green zircons without a muddy brownish green appearance are even less common, and I’ve only seen zircon triangles in custom-cut stones. But fortunately, my leg-work paid off and I was able to source a large, if misshapen, green zircon triangle.
The stone started out as a 7.10ct squat triangle measuring 12.48×11.04×6.80mm. It wasn’t a bad stone in hand, but the original cutter was clearly shooting for maximum yield at the expense of beauty.
I requested my client spend some time poking through my online portfolio over on Flickr. Wisely, he decided to look through things with his wife (spoils the surprise of the gift, but avoids disappointment) — they decided they like the looks of a custom barion trilliant I cut from a choice Afghani tourmaline nodule (http://www.flickr.com/photos/ptorraca/8761160402/). At first I was hesitant to use that design because it would require losing a good portion of the existing stone to those straight sides. But now that the stone is completed, I think they made a good choice:
Green Zircon. 4.11ct, 9.21×9.16×6.71mm. Untreated. Inc1. Barion Triangle, Crown #3. (Zir869)
I’m really looking forward to seeing pictures of how my clients mount the stone. It’s a fantastic gemstone and should prove a great conversation piece for them.
Can I help you with a custom cut gemstone?
Worthwhile links about zircons & radioactive inclusions:
http://www.gemologyproject.com/wiki/index.php?title=Zircon (zircons in general)
http://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?t=8748 (interesting details throughout discussion)