Saturday, July 21, 2012

The Fading Beauty of Spodumene

With so many interesting and neat gemstones on the market, knowing what's what can get very confusing.  But some information should still be made more public!  Kunzite is a pink gemstone that has gained some recent popularity.  It is part of the family of Spodumene, which also includes a green variety called Hiddenite (colored by chromium), as well as clear and yellowish stones.  The specimens are large, prices are low, and the gem is very pretty in general.

So I decided to buy a parcel of mixed colors, straight from Pakistan via EBay – yes I use EBay on occasion, but it is not for the uninitiated.  But that’s another blog entry….

My parcel arrived quickly and checked as spodumene on the refractometer.  The price was great, too.  I made a couple of pendants right away.  Then I went to an outdoor craft fair.  A few days later, I noticed that my pretty green gem had faded to a pinkish white, sort of like a very washed out morganite.  Someone on Etsy was interested in it, I discouraged the sale to buy myself some time.  I asked around.  Yes, the stuff can fade, I was told, especially the greens.  So I put that in the description, and planned on re-photographing the piece, or just selling it as the pink variety, kunzite, describing it as very light color.  Before I got around to it, someone else bought it.  I apologized profusely, and reversed the sale upon explaining that this was no longer a necklace with a green gem.
Spodumene Piece Before The Color Faded

On the Right, the Spodumene After the Color Faded, Next to a Difference Piece (Also Faded Now)
The very gracious customer went onto Google and tried to get more information.  Websites turned up that claimed it was an “evening” stone, had to be stored in a bag and only worn at night because it fades in sunlight.  (What a pain… ) Other sites said only the green fades, yet other sites said they all fade, and one site said it fades only when it is heated.

I finally went to GAL and asked for clarification.  My friend there consulted some more reputable GIA sources and books.  I asked him to tell me which of the following claims are true, and here are the answers.
“1. Only spodumene that was heated to make green stones fades.”
Trick question:  False –  you get Green from Pink from irradiation by x-ray or gamma ray, not heat.  Any type of Spodumene that does NOT contain chromium will likely fade …but can be reversed and “re-reversed” via irradiation. 

“2. Only irradiated stones fade.”
False – This is just innate in spodumene in general, except with a high presence of chromium, which stabilizes the stone for some reason.  This has something to do with the valency of the electrons in chromium and how it reacts to the other transition/metallic elements such as manganese. 

“3. All spodumene fades.”
False – See above for exception.  Everything else most likely will fade though.

“4. Most spodumene fades, both pink and green.”
True – Most spodumene will fluoresce, phosphoresce, and it usually has the phenomenon called "tenebrescence", which is the technical term that causes the color to fade. It does not fade ONLY if chromium is present.  Chromium bearing spodumene can still be irradiated to alter its color though. 

In addition, here are the most common treatments of spodumene and their results:
Using X-ray or gamma ray (irradiation) can turn pink to green
Using only X-ray can turn colorless to pink and then to green (this can be stopped at stages)
Using Daylight/UV/Heat or equivalent can turn green to pink and to colorless (this can be stopped at stages)
So most likely my green stones were not chromium bearing and had been turned from pink to green via one of these treatments.  Which I then accidentally reversed by exposing it to sunlight.  

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