View Full Version : Plastic ,Glass or Stone ?

24-11-2017, 07:39 PM

My gem knowledge is incredibly basic. I'd love to have gone on a Gemology course but I joined in this wonderful trade far far too late to consider doing a gemstone course as well as learning the entire making proccess from the begining.

I however, have got access to a digital refractometer, this helps massively but I got totally stumped the other day, as the batteries ran out and I had no replacements, a customer turned up looking to sell a ring and I had no way of knowing what the "Stone" was.

One was a Black cabooshon oval stone and the other a flat Black signet ring set stone.

My guess was they were Onyx, so based on this I made the guy an offer, explaining honestly my inexperiance and he was happy with the price I offered.

He did tell me, he couldn't be sure if the stone was Plastic,Glass or Onyx....So without a refractometer, is there a way to tell these apart easily ?

Thank you

24-11-2017, 08:40 PM
Yes, but he might not have liked it. Plastic will burn, and glass will melt. The essence of a good deal is that both parties are happy.

On a more serious note, there is a myriad of black stones as seen in the link below, but the metal of the ring would give a clue as to the order of value. In fact it might be the only valuable thing about it. So a hallmark would be the first thing to look for.

https://www.google.co.uk/search?q=how+to+differentiate+between+black+gemsto nes&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&dcr=0&ei=XZUYWovqAenGXoqYsLgL Dennis.

25-11-2017, 05:55 PM
Thank you....But without damaging the sellers property, is there any way to tell if the "Stone" was either Plastic,Stone or Glass ? The rings were 958 Silver hallmarked.