What is this stone?

[purplesparklies]

I have a stone that was purchased in Greece in 1970. It was purchased at a high end jewelry store. It is a large round stone that has a really interesting cut that shows a flower-esque shape when you look at it from the top. It is a color change stone that changes from a gorgeous green to blue-green to deep blue to deep purple to amethyst purple and even a purple-y wine color. It is eye-clean but a local jeweler put it under a scope and says it is full of lines, straight lines. Now, I realize that it is not going to be natural alexandrite based on the size and clarity. However, I would love to know what it is. In my own amateur research I've read that the most likely answer is corundum but sources have said that will contain curved lines, not straight. Also, from my reading it will go blue but never green. This stone definitely gets green. The greens/blues come out in natural light, the purples/wines are in various indoor lighting. Local jewelers are of no help. They just want to give me the "synthetic alexandrite" at first glance but are uninterested in my helping me identify it specifically. Thanks so much for your help!

 

[VapidLapid]

It sounds like you have local jewelers who are significantly less than amateurs. No one can tell you online even with good photos what it is you have. laboratory tests are needed to make a proper determination. If you think the stone is valuable you should get a report from GIA or AGL or any reputable lab. One would need to have more information about these curved or straight lines for them to indicate anything, like do they look like growth lines (eg. synthetic) or silky inclusions (natural rutile). Regardless it is beyond the scope of an online forum to conclusively identify mystery stones.

 

[Michael_E]

Regardless it is beyond the scope of an online forum to conclusively identify mystery stones.

Not so, I happen to have one of these and it's always right.
Magic 8 Ball says, "Probably a synthetic corundum, since curved growth lines can look straight to someone who's not paying attention...see a gemologist anyway to be sure". I know you're going to ask so I'll answer your question beforehand...yes, I do have one of the new "scrolling" Magic 8 Balls, I'm getting much better answers that way.

 

[LD]

There are, unfortunately, a number of synthetic types of alex on the market - and in the 1970s it was extremely common. You've said two things that make me suspicious however (1) large/eye clean/strong colour change - this is very rare with natural alex and you would most definitely have a very valuable stone in your hands if this turns out to be natural and (2) that it shows blue as one of the colours - this is indicative of a simulant/synthetic.

Czochralski alexandrites (sometimes called pulled alexandrites) have straight inclusions but with a small bulb on the end - think of a tadpole! The tail is very long and I wonder if this is what you're seeing? Interestingly I have a Czochralski that behaves in the same way you describe. There was aboslutely tons of it floating around in the 1970/80s and it was sold in Egypt to tourists (i.e. alexandria = alexandrite) to fool tourists! Of course it was sold elsewhere but if this stone was bought in the Mediterranean it would certainly fit the timescale and part of the world that this was commonly found. This type of synthetic alex can most definitely show the blue that you're seeing AND will have a range of colours and a strong colour change. If I was a betting person, I'd put my money on this being what you have!

Flux grown alexandrite tends to have flux residue that can mimic inclusions in a normal stone and this is the variety that is very difficult to spot. Typically it has inclusions that you can see (rather than just with a loupe) and these ones tend to behave like alexandrites and even look like them. In this type of simulant, strong banding or growth lines may be seen and some even have parallel negative crystals. Because flux grown alex shows inclusions, this type really need to be tested by a lab. One of the give-aways though is the strength of colour change. Despite what you may have read, an alex with a very good colour change from green to (typically) purple/red, is not common. Weaker colour changers are easy to find. So if you find one that behaves as you've described the changes are you've either got a synthetic OR you're a very lucky person!

Synthetic corundum laced with vanadium has often been sold as Alex - but as you say, it very rarely shows blue. It's easy to spot the difference here because it will have a refractive index of 1.759 - 1.778 rather than a chrysoberyl reading of 1.741 - 1.760. If your jeweller has a spectroscope, this type of corundum has a strong vanadium absorption line at 475 nm. So this type should be easy to rule out. Many jewellers can test the RI of a stone so that could be a good starting point.

Synthetic alex can have curved striatia, gas bubbles, flux inclusions, liquid feather type inclusions, triangular metal platelets and a smattering of what appears to be dust captured within the stone amongst others!

Lastly there is also a synthetic now that mimics the exact chemical composition of natural alex - these can only be weeded out with laboratory testing.

BTW, in a real alex you typically can see a range of inclusions but most common are silky rutile inclusions (that can make the gem look cloudy in places but enhances the colour change) and fingerprint inclusions - unfortunately many gems also have internal fissures that will be reasonably evident.

You haven't said how large your gem is but if it's over 1ct then, as you say, it may be another giveaway that it's not natural. I do hope it is however - that would be a lovely start to 2011!

If you do find out, please come and post again won't you - and pictures would be nice for those of us who love to see eye candy!!!

 

[purplesparklies]

I appreciate the knowledgeable responses. I understand that I won't get a definitive answer via a platform such as this. However I also know that there is a tremendous amount of information available from the experts who graciously share with those who have developed a passion for the beauties available on the market. Czochalski alexandrite is sounding suspiciously accurate. I would say this stone is several carats in size. If the answer is Czochalski, what is the worth of a stone like this? I have grown rather attached to the beautiful color change and many Czochalski I've found online describe a much less dramatic color change. I bought this one but it was purported to be natural alexandrite. I knew it wouldn't be but I was dying to see the color change that was described. I can certainly return it and get a full refund but it's just so pretty! Where can I get the best deal on something like this with the full range of dramatic color change? I'm having such fun with the changes....

 

[LD]

I appreciate the knowledgeable responses. I understand that I won't get a definitive answer via a platform such as this. However I also know that there is a tremendous amount of information available from the experts who graciously share with those who have developed a passion for the beauties available on the market. Czochalski alexandrite is sounding suspiciously accurate. I would say this stone is several carats in size. If the answer is Czochalski, what is the worth of a stone like this? I have grown rather attached to the beautiful color change and many Czochalski I've found online describe a much less dramatic color change. I bought this one but it was purported to be natural alexandrite. I knew it wouldn't be but I was dying to see the color change that was described. I can certainly return it and get a full refund but it's just so pretty! Where can I get the best deal on something like this with the full range of dramatic color change? I'm having such fun with the changes....

Can you really get a refund if you bought it in 1970??????

Ok, to give you a few ideas ............. a 2ct natural Alex with great colour change (of about 90%), eye clean, would be considered a very fine gemstone indeed and would probably cost (loose) anywhere between $10-15k depending on the colour change, cut, clarity. I realise that's a very wide ballpark but the strength and amount of colour change is the over-riding factor with Alex.

A synthetic or simulant I'm afraid you could pick up relatively cheaply - most definitely for under $500 (and in all honesty it should be much less). Having said that, if you only paid a few hundred dollars and you love the ring then keep it. They're very pretty and finding an alex of the quality you describe would mean you'd have to dig deep into your bank account.

However, if you feel you've been missold and that annoys you then you should send it back BUT before you do, you need to get the stone checked out by a lab (not an appraiser) to know for sure. Most jewellers will never have seen alex and even if they have, they won't have seen a significant amount to be able to give you anything other than a guess so you really need a lab to look at it. You don't want to say to somebody that they've sold you a fake unless you have proof. If you suspect it's not natural then contact the vendor and ask for an extension on the return period while you get it checked out. A good vendor will always take something back if it's not as they sold it!

 

[purplesparklies]

Purchased from an individual who purchased it in 1970. As I said it comes as no surprise that it is not as described re: natural but I do hate to feel as though I'm supporting someone who is passing off fake as real. However, I do believe that the seller truly thought it was what they had been told so many years ago. Plus, like I said, I'm enjoying the fun of this quirky little ring. I paid $200 and it's roughly 12mm so a good size stone. I want to keep it but don't want to feel like a total idiot for paying $200 for something like this. I'll probably keep it because it is unique and fun. Thanks again for the excellent information.

 

[LD]

A 12mm alex is about 5 or 6ct!

For $200 you've paid a fair price - especially if you love it.

I understand exactly how you feel and the original seller is very naughty. Anyway, just enjoy your pretty stone. It sounds lovely!

If you get a spare 10 minutes, do a search for Alex on this forum and you'll see some lovely examples!

 

[m76steve]

for a reference - here is pics of lab alex in daylight & incandecent light [top]-steve...

 

[chrono]

I agree with LD that the words large, eye clean and strong colour change rings many alarm bells on my synthetic radar. Since you paid only $200 for it and you like it, then keep it. It is most likely to be synthetic alexandrite as LD as advised based on the limited information we have.