Thursday, November 15, 2012
Most of the previous articles dealt with heat treatment although I did get into some other ones for diamonds. Other types of treatments however are used in a lot of cases and should be noted. Irradiation is used on a lot of gem materials today. The most well known stone this is used on is blue topaz in which a combination of heat and irradiation is used to get a variety of blue colors. About 95% of the blue topaz on the market today has been treated. Tourmalines are also irradiated sometimes and also occasionally it is used in conjunction with heating. Freshwater pearls have also been irradiated to change the colors on them. Oiling is a common treatment for emeralds. This has been done for a long time as the oils used hide some of the inclusions in the materials. Fracture fillings are substances that are applied under pressure to some gem materials. Emeralds have been subject to more of this than most stones, again because of the nature of the material, but there are also fracture fillings used on diamonds. Bleaching is used often, especially on pearls. There are also a lot of gem materials subject to dying which can include materials like pearls, turquoise, lapis and I have even once seen sapphires that had been dyed. Opals can be dyed, treated with smoke, treated with a sugar and acid mix and impregnated with various substances. Agates are often dyed. The list goes on and on actually. If you would like to spend some time looking at a full list of gemstones and treatments you can go to this link: http://www.agta.org/gemstones/agta-gim/index.html. This is a book put out by the American Gem Trade Association that lists every gem and possible treatments.
So the question, of course, becomes what is a layman to do about this when buying gems. The first thing of course is to buy from someone you trust and where you have recourse if the goods don't turn out to be what you are told. In other words don't go spend a ton of money when you are overseas on a trip, since you can't exactly return it easily. The second thing to remember is that if it sounds too good to be true then it probably is. If someone is offering you a two carat ruby for $200, then that's exactly what it's worth. It's not going to be worth $20,000.
Then there is the broader question of whether you want to buy treated gem materials or not. With something like tanzanite, you really don't have any choice since it's all treated. Emeralds are the same although there are occasional pieces of untreated material. My personal belief is that, with the exception of emerald, if a colored gemstone treatment is permanent and is not introducing a new material into the gems then it is acceptable. My preference on things like diamonds is that since so many natural untreated stones are available there is absolutely no reason to sell ones that have been enhanced in any way. Everyone however has to set their own boundaries and sometimes price enters into the consideration. If you only have $100 to spend on something and you like a dyed agate piece, then go ahead and buy it.
You should all note that I have not dealt with synthetics or simulants in this series of articles but I will save that topic for a later date.
The earrings pictured above are 18k and 22k yellow gold with all natural sugilite in them.