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.  

Friday, July 6, 2012

Idar Oberstein - Round Two

As many of you know, I went back to Germany (and also Italy) for part of June and July, visiting family and taking a much needed break from work and jewelry. But what would a trip be without at least a little gem shopping? So I made another appointment with the Sri Lankan in Idar Oberstein who sold me those awesome spinels last summer.
This time I took my dad along for the ride. Ulterior motive: the drive Idar-Oberstein, one of Europe's main gem trading centers, is 2 hours each way. But dad had fun watching me pick out gems, pair them up on the ridge between my index and middle finger, loupe for inclusions or cracks, while he was sipping tea and trading news about world economics with Rohan, the gem dealer.

Rohan told us about a new mine near Kataragama, Sri Lanka, which was discovered at a construction site.   The mine produces Kashmir like sapphires, but with lots of color banding, so cutting has been challenging. Prices have already skyrocketed because of the Chinese economy. Apparently, many gems are being sold in Hong Kong, and fewer arrive in NY an Europe - which I can attest to, not having had access to good sapphires in over a year. Mohammed, my previous Sri Lankan source, has essentially vanished. Probably he, too, goes to Hong Kong now. Rohan, meanwhile, did buy two pieces from the new mine for a customer, but these stones are not anywhere near our price range.

Nevertheless, I lucked out as well, because some of the cute spinels Rohan had cut over 10 years ago were still available: little hexagons, square emerald cuts and trillion cuts. The smaller pairs will appear in my shop for about $75. But I also got reds this time and one or two larger pairs, which will cost more.  He increased prices a little, but within reason.

Ceylon Spinel Pairs

I even got a pair of 5mm hexagon green zircon and two pairs of chrysoberyl, all from Sri Lanka. In spinel, I got a lot of blues and reds, some pinks but very little purple. I also got one larger purple gem, about 3.5 carats (see the picture below).
Ceylon Spinel, About 3.5 Carats
But mainly I was interested in buying sapphires. I had hoped, and I was right, that Rohan might have some pieces stashed away that were mined and cut a while back. Ceylon sapphire, you should know, has to be cut in Sri Lanka before it can be exported. Some cuts are nice, some are not. Also, much of the material is lighter in color, so it is either heat treated or cut with a bulky pavillion for color retention, or both. I wanted the unheated of course, insofar as possible. It took two hours in total, but I eventually settled on 5 small dark pieces under one carat (one or two of these might be heated, I'll find out when I get back - heat treatment is checked under the microscope), one larger unheated medium blue (about 3.45 carat), and two large yellows, 6.31 carat or so total weight, for an awesome introductory price.

Ceylon Sapphires Under 1 Carat

Yellow Ceylon Sapphires

Large Ceylon Sapphire, 3.45 Cts
I had to pay cash - that was a drawback but this is to be expected when low prices are made. For a seller like Rohan, who usually deals in large stones only (both for private clients and for jewelry stores), who has no internet shop, no store and who does not do shows, a customer like me means quick extra money made with materials that don't see the light of day very often. Materials, in other words, that are not of interest to larger jewelry stores who want new cuts, certificates and appraisals.

In the right circumstances, therefore, this can be a win win situation. I know my sapphires very well, I know the NY market, and I know how to work with gems that don't have perfect cutting. So I think I will do well with the pieces I got, and so will you if you're interested (even though none of them will be cheap). I just wish I could go to Germany more often. There were a lot of gems I wanted to have but that had to stay behind because as you can probably surmise, I totally blew my budget for the time being. You'll have to wait a bit for the sapphire listings in the shop, but further inquiries are welcome. Before I make any prices, these babies are going to the lab. I'm fairly sure my purchase and prices were good, the seller reliable, but values change constantly and I want certainty.

Red and Pink Ceylon Spinels, Some Pairs