How can you tell if alexandrite is real/natural or lab

[Kostarica157]

I was trying to see if someone could help me determine if my stone which I believe to be alexandrite is actually a natural alexandrite or lab created or not alexandrite at all. I have put it In natural light and also under uv light in these photos all help is greatly. Appreciated. Also if anyone knows a good reputable gemologist in the northern California area of you could give me there info. Thank you. If you want to send a private email you can send it to greek157 at hotmail . Once again thank you for the help.

 

[Kostarica157]

 

[Pandora II]

The colour change in fine alexandrite should be from a teal-green in daylight to a rasperry in incandescent light.

A lot of 'Alexandrites' - especially the bargain ones in junk shops and the ones left to you by your great grandmother - are in fact synthetic colour-change corundum (sapphires) and tend to be a change from a blue-purple to a purple-pink. They never show any green.

A gemmologist can easily separate sapphire from alexandrite - they have very different refractive indices for a start. The colour-change synthetic corundum owes it's colours to the element Vandium, whereas alexandrite is coloured by Chromium. The corundum will show a very distinctive spectrum due to the vanadium. Stones also tend to be clean but may contain gas bubbles or curved striae.

There are several types of synthetic alexandrite available. Those grown by the crystal pulling method are relatively easy to spot as they tend to be very clean and have give-away signs like curved striations and rain-like inclusions under magnification.

Those grown by the flux method are a different animal. They are expensive to produce and contain inclusions that can look very similar to the real thing (this isn't a scam, it's just the way that they grow) plus the colours tend to be more like the real thing.

Synthetics will have the same optical, physical and chemical properties as the natural and you will need a good lab to identify it. There was a recent case where AGL picked up a synthetic alexandrite that GIA had said was natural, so it's not always an easy task.

Natural alexandrites under UV tend to fluoresce to a much lower degree than the synthetics as they contain iron which is a natural supressor of fluorescence. A chalky yellowish-orange under short-wave UV is, I have been led to believe, indicative of some types of synthetic alexandrite.

Hope that helps a bit. If it's a vanadium coloured CC synth. sapphire or a pulled-crystal synth. alexandrite you may be able to tell fairly easily yourself with a loupe. Otherwise it's a job for a lab.

Btw, we are not allowed to give out email addresses here.

 

[LD]

Pandora's advice is spot on. One thing I would add is that some synthetics / imitations are so good that ONLY a lab can give you an absolute answer. I bought one that looked right (great colour change, colours were correct in all lighting conditions etc etc) but something just didn't "feel" right. Several gemologists looked at it and not one wanted to say 100%. I sent it to a lab who confirmed it's wasn't the real thing Bottom line, send to a lab!