Determining Natural Amethyst from Synthetic

Since readily available synthetic amethyst nose dived the market in the 80's it's been very hard to tell the difference between the synthetic and the natural forms. Some estimates suggest over 90% of what comes to market now is synthetic. Both are often free of any telltale inclusions, but I came across this posted on a jewellery forum.

https://www.gia.edu/doc/A-Simple-Pr...nthetic-Amethyst-on-the-Basis-of-Twinning.pdf

I'm not sure 'Simple' is the best description for people at home (for a lab maybe more so), but it is possible. I don't have any unmounted well cut amethysts to test so I had to use mounted stones, the bigger the stone, the easier it is. I couldn't get it to work with a polariscope, possibly as the mounting was a big hindrance, also I couldn't get enough visual acuity on it.

So I bought two polarisers for my microscope, one for the objective the other to polarise the transmitted base light. It worked, cross polarised and angled through the right plane I can see the Brazil twinning in a natural stone, no immersion needed. It takes a bit of time to get the hang of, and I found a magnification of about 20x worked best (stones of 1-3 carat). I don't have any at the moment but it is supposed to work on ametrine too. This test doesn't determine if it has been heat treated though.

All it cost was two cheap polarisers from ebay (£17 for a 55mm and a 95mm that I needed for my setup) and now I can ask a premium for natural stones over synthetics, so it will easily pay for itself in one sale. If you have a microscope as long as you can get the polarisers in place you should be able to do it as well. Certainly worth a try at the cost.

 

Never knew quartz had chirality.

 

Isn’t that something to do with knights in shining armour?
Off to google the word now I’ve exposed my ignorance again!

 

Using a microscope to study gems is on my wish list however I have so much to do before I get to have the free time to do that I will just have to live it through here. @Ce BCA please do post anything interesting as I for one would be interested.

 

maybe schiller?

 

I’ll google that too.