QuestionI have an 18 carat gold signet ring with a blue stone in in that the jeweler said was a saphire, how can I tell if its genuine or not?
AnswerFake gems are sometimes very close to the real thing in terms of appearance, refractive index, and even the reactions they provoke when tested.
I'm more of an expert on emeralds, but some very basic tests can be done an many types of gems using a Chelsea Filter, which can be purchased for $35-$50 on Amazon.com or direct from jeweler supply vendors. It however is not going to tell you definitively if your sapphire is real. Only a trained gemologist can do that. They'd do several tests that may involve a microscope, dichroscope, UV light tests, refractive index tests, and several others they can do. Many times, just a quick look under a microscope will give a very good idea if the stone is fake, but of course you have to know what you're looking for. To give you an example, I had several rubies sent to me by a friend working in Afghanistan last year. He sent several large stones over 5cts with a very dark color and several smaller ones with a lighter color. It took just 5 seconds with a microscope to detect bubbles in the large stones. Obviously they were fakes and we found evidence of fracture filling in the smaller rubies. They were real, but they were of very poor quality, so we sent them all back.
I should note that most of the employees you'll find at jewelery stores are notoriously bad with gems. Even many jewelers themselves are not very well informed or educated on the subject. This may be very surprising, but personally I've found very few that really knew what they were talking about on subjects other than gold and diamonds.
