People sometimes email us photos of gemstones and ask us for help in identifying their stones. We try to be helpful, but even the best gemologist in the world can't definitively identify a gemstone from a photograph. Even visual inspection of the actual gemstone is rarely sufficient.
The systematic study of gemstones has come a long way since the days when any attractive red stone was called a ruby. Today gemologists have to be able to identify hundreds of varieties, as well as detect an ever-growing list of gem treatments and synthetics. What once was an art has become a science and gemstone identification without careful measurement is just guesswork.
Every type of gemstone has a unique set of physical and optical properties. These include not only color and luster, but also hardness, specific gravity or density, and refractive index. Though several type of gemstones may have approximately the same specific gravity or the same specific refractive index, each gem type has a unique profile when results of all the basic tests are considered. Just don't try to identify a gem by refractive index alone! You could very easily be wrong.
Every gemstone has a unique set of properties because minerals form in different environments in the earth. They are known to geologists as igneous, metamorphic and sedimentary rocks.
The basic gemological tools are not difficult to learn to use. They include the simple 10x loupe (a powerful tool in the hands of an expert), the refractometer (for measuring refractive index), the polariscope (for identifying singly and doubly refractive gems), and a scale accurate to the 1/100th of a carat (for measuring specific gravity). You can learn to use these tools by attending a gemological course or even through self-study and experimentation.
GemSelect is a leading online dealer in fine gemstones, specializing in sapphire, spinel, tourmaline and zircon. Large Gems
