As a company which specializes in natural untreated sapphires we often receive letters from our customers. The answers to their questions I feel are beneficial to anyone who is interested in purchasing gemstones.
Recently we received this letter:
Hello: I recently purchased a stone through you and I am quite happy with it.
I do have a few questions, however. First, you make the claim that certain sapphires “show no evidence of treatment.” I understand that it is easy to tell if a gemstone has been treated, but not so easy to tell if one hasn’t. Can you explain to me how you make these judgments, perhaps what tests you use? What makes you confident that they are not treated?
American Gem Trade Association, AGTA, Certificate
There are many tests that are performed which look for certain treatments, however the best way to determine if a sapphire is untreated is under the microscope. The most common treatment is heating and this is preformed on over 95% of sapphires in the industry.
Under a microscope you look at the natural inclusions which occur during the crystals growth. If the inclusions are undisturbed then that is how we can determine that there is no evidence of heat treatment. Natural inclusions such as silk and crystals will have a severely different appearance after treatment. In treated stones, the silk (a type of inclusion named for its appearance) will be broken and diffused. The heat will cause any fluid inclusions to rupture, crystals or mineral inclusions will break up and will often form a fracture around the crystal which we call a halo.
For other treatments such as lattice diffusion there are different equipment that test the stones for its element and concentration properties, also the microscope is a wonderful tool here as well. The sapphire would be viewed while submerged in a special liquid which helps see if there is a strong concentration of color around the edge of the stone and to what depth the color penetrates. A stone can have a stronger concentration in a particular area, however the concentration will be throughout the stone. Certain diffusion treatments such as Beryllium treatment does penetrate further into the stone, so there are specific tests that are run to determine that it is not treated in this manner.
Images Provided by John Koivula
Please email any jewelry or gemological questions you might have to Info@TheNaturalSapphireCompany.com and we will be happy to share the questions and answers with all gem enthusiasts.