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| Using a Spectroscope |
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The spectroscope is used to analyze light passing through a stone. White light is a combination of all the colors of the visible spectrum: red, orange, yellow, green, blue, indigo, and violet. This is the rainbow we see when light travels through a prism. When white light travels though a stone, one or more of the wavelengths that produce color are absorbed by the gem. The colors that are NOT absorbed are the colors see when we look at the stone. The wavelengths that are absorbed by the stone are seen in the spectroscope as verticle black lines in the spectrum. Each stone has a unique absorption spectrum (like a fingerprint of the stone) When identifying a stone we look for a spectrum that is characteristic for that stone. |
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 Absorption spectrum with proper lighting & no gemstone. |
Using a spectroscope takes practice! Try using it in different lights, with different stones. It takes some time to learn what you are looking for and what those little fuzzy lines mean. What you actually see through your spectroscope will not (!) Be as clear and pretty as what you see in books are charts. |
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You will need a list of spectrums to compare your finding to. There is a chart of common gem in the Gem Facts
section on PrettyRock.com. Or we highly recommend one of the following books available on PrettyRock.com: The Spectroscope & Gemmology Gem Identification Made Easy A Student's Guide to Spectroscopy Light Source: It is important to choose the appropriate light source when using a spectroscope. If you don’t you end up with the absorption spectrum of the light, and not the stone. To check a light source, simple look through your spectroscope. If you see vertical lines, it’s not a good light to you. The easiest way to use a spectroscope is to create a restricted light source using a strong flashlight and some black construction paper: |
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1. Cut out a rectangle long enough to wrap around your light source, presumably an LED light or a maglite. Now, tape one end of the rectangle piece to the light, and wrap it around and tape the other end to the light creating a tube around your light source.
2. Cut out a circle in your construction paper. (Trace around a jar lid works or other similar size circle. Cut a line to the center of the circle. Then fold the circle two ways and cut to the 'X' crease. Now crisscross the two edges the cut made and the circle will rise up into a cone or funnel shape. Tape the cone at the desired angle or depth for your use. Snip off the tip of the cone to allow light through. Keep it small, but you may need to adjust it given the strength of your light or the size of your gemstones. 3. Set the cone, tip first, into the paper tube on the light. The stone is placed into the cone. Mineral tack can be used around the girdle of the gem and pressed it into the cone base so that you have a really tight light source seal. 4.Bring the spectroscope and your good eye up to the gemstone and find a good position for seeing the spectrum. Try turning the light source with the tube/cone/gem in place until nice bright flash of light from the gemstone. Put the spectroscope over that light flashing off the gem and bring my eye to it to see the fully illuminated spectrum given off by the gemstone. |
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Absorption Spectrums for Common Gemstones Below is a quick reference of simulated absorption spectrums for common gemstones. There are many different signature spectrums within each type of gem depending on locality, depth/saturation/hue of color, and of course the specific chemical impurities that happen to affect the gemstone's color. This quick reference gives you a generic idea of what light frequencies will be absorbed for each gemstone. We strongly recommend purchasing one of many great textbooks in order to comprehensively and accurately identify your gemstones. The wavelength nanometer scale (the numbers below the spectrum) is below the spectrum. NOTE: Most spectroscopes do NOT include a wavelength scale. That is a feature reserved for expensive professional equipment. The absorption lines have been stretched above the spectrum for quick and easy reading. |
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Blue Sapphire | |
Ruby | |
Emerald | |
Aquamarine | |
Blue Spinel | |
Red Spinel | |
Peridot | |
Rubellite Tourmaline | |
Blue Green Tourmaline |
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| The most popular guide to identifying gems and synthetics. Essential reading for collectors, dealers, and students to avoid mistakes and recognize opportunities. Authors: Antoinette Matlins and A.C. Bonanno Hardcover. 330 pages. -B0676- Click for more info. |
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