Identifying A Colored Gemstone

One of the more challenging assignments a gemologist may have is to correctly identify colored gemstones, usually for appraisal purposes. At first thought this may seem like an easy task. As a matter of fact, there are many people who have worked in the fine jewelry industry for years that cannot correctly identify colored gemstones, I have worked with many. Identification first starts with a clean stone under a 10x gemscope. The color(s) throughout the stone and the type of inclusions offer a hint of what the stone may be. Another test using a Refractometer, which tests the gemstones ability to slow down or bend light, also aids in the id. Without getting to technical, the amount of slowing down of light it does is referred to as the Refractive Index (RI). The RI along with what was found, and not found, in the gemscope can lead to an identification. There are several other tests that a gemstone could undergo in determining what it is, but again, to keep this from getting to technical, we will just stay with these two tests as they are the most important.

In order to complete the requirements for a Colored Gemstone Graduate degree from the Gemological Institute of America, the final exam is to correctly identify twenty gemstones. A very taunting task I assure you. Let’s have some fun and see if you can pass a three stone test.  From the three color groups below, pick out a Ruby, a Sapphire, and an Emerald.

Which is the Ruby?






Which is the Sapphire?

blue-sapphireblue-spinel kyanite





Which is the Emerald?






Left to Right:                                                                                                Red: Ruby, Pyrope Garnet, Red Diamond                                                  Blue: Sapphire, Blue Spinel, Kyanite                                                       Green: Chrome Diopside, Emerald, Tsavorite Garnet

So how did you do? Pyrope Garnet, Blue Spinel, Kyanite, and Tsavorite Garnets can be found in numerous pieces of fine jewelry, usually only found in specialty/designer fine jewelry stores. A Red Diamond is extremely rare and you will probably only see one in photos. Chrome Diopside is great for the look of an Emerald but at a much lower price, however it is not commonly used.

If you are looking for a particular piece of jewelry, unless you really want a specific stone, you may want to be open minded about what Mother Nature has to offer. After all, not all blue stones are Sapphires and not all Sapphires are blue!