Advanced Gemology Topics

Advanced gemology topics on a wide variety of technical subjects such as gemstone treatments and inclusions.

Advanced Gemology Topics

  • gemstone color change - stillwellite
    Gemstone Color Change Phenomena 

    Frequently, people ask me to explain how gemstone color change works. Some stones can change color under different light sources. Although the answer is pretty complex, a few diagrams can really help.

  • D3 (1)
    Gemstones and Refraction Liquids

    Liquids with a high refractive index (RI) are used in gemology to evaluate the refractive index of a gem or to separate one from another in a bundle. Another use is to allow a clearer vision of any inclusions in a gem while it is immersed in the…

  • HPHT Diamond Update 

    Step 2: Advanced Gemology Lesson 8 Back to syllabus Synthetic Diamond History High Pressure High TemperatureDiamonds were first synthesized from graphite in the 1950s by the high pressure high temperature (HPHT) process. In…

  • “Quartz with Petroleum Inclusions” by Luciana Barbosa is licensed under CC By-SA 3.0
    Identifying Inclusions

    Magnification opens the door to a fascinating dimension in gemology: the inner world of inclusions, materials trapped inside gemstones. You’ll see marvels that can rival the beauty and intrigue of the gem itself. On a practical level, identifying…

  • Figure 1
    Measuring a Gemstone RI above 1.81

    by Raul Berenguel, PhD The determination of a refractive index (RI) above 1.81 can be a problem for several reasons. While you could use an electronic refractometer to measure a gemstone RI, it would be expensive because the low-cost models do…

  • impurity ions - red beryl
    Impurity Ions and Gemstone Colors 

    I’ve faced many questions about the element chromium (Cr), the red coloration of minerals, and the gemstone red beryl. One of the many causes of color in gems and minerals is impurity ions.

  • gemstone radiation - quartz
    Gemstone Radiation Treatment 

    Most gems on the market today receive various treatments to change their natural colors and create more desirable, salable products. Radiation and heating are the most common treatments, used alone or sometimes in combination with other enhancements.

  • rough-quartz-images-urg2_5
    The History of Quartz Treatment

    Recently there have been questions about a treated quartz with a light yellow/green color similar to chrysoberyl. The material is traded in Brazil under the name Ouro Verde. I am actually the one who developed the process. In this process, the gem…

  • conc2
    The Physical Properties of Gemstones 

    Step 2: Advanced Gemology Lesson 2 Back to syllabus It is the optical properties of gems that attract our eyes and give them their unique character; however, the physical properties of gemstones are also of prime importance. It…

  • Rose Quartz Stone
    Treating Quartz to Create Color

    Some, but not all, clear quartz  can be treated to create numerous colors using irradiation and heat treatments. When treating quartz, it is possible to achieve a range of colors, depending on where the quartz came from and how you treat it. Here…

  • vacpis~1
    Understanding Emerald Enhancements and Treatments

    Because most emeralds are highly included, they are very often subjected to a variety of treatments to enhance their visual appeal. Emerald treatment consists of numerous types of fillers, impregnations, and dyes. The purpose of which is to make…

  • mexican-opal-01_1200px-no-mm_905
    Gemstone Photomicrography and Inclusion Photography

    In 2004, while a student at the Gemological Institute of America, I opened the Photoatlas of Inclusions in Gemstones Vol.1 for the first time. I was looking for a career change and, while I didn’t exactly have a plan, I knew I was burned out in my…

  • inc63
    Identifying Inclusions of Specific Gems 

    Step 2: Advanced Gemology Lesson 12 Back to syllabus Beryl and Tourmaline Both beryl and tourmaline develop hollow, or “growth” tubes. The gem cutter sees many more of these than the gemologist does, as most are cut away. While…

  • Identifying garnets by species can be difficult due to the great variety of their chemical compositions and properties. There are even stones with mixed compositions. A rhodolite is a garnet with a composition between almandine and pyrope with a distinctive purplish red color. “Rhodolite,” 3.63 cts., fancy round brilliant cut, Tanzania. © Dan Stair Custom Gemstones. Used with permission.
    Identifying Garnets Simplified 

    The most complicated part of identifying garnets is distinguishing between the species. The gems in the almandine, pyrope, and spessartite series are particularly difficult separations. However, the following chart will simplify the process once…

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