Mystery Relating Gemology Unveiled
Gemstones are a marvel of nature that are dazzlingly graceful and gorgeous. Every gem is unique with certain unique characteristics that establish its value and worth. When buying jewelry or watches containing these gemstones, the service of a trained and certified gemologist is required to ensure you are getting the real deal. These experts are trained in the field of Gemology that is a science in itself.
What is Gemology?
Gemology is a science that involves appraising natural and artificial gemstones. It is the study of optical and physical properties of gems to appraise their merit and worth. These properties distinguish one gem from the other and establish their authenticity and value.
The National Association of Goldsmiths of Great Britain (NAG) in 1908 was the first institute to train individuals in the field of gemology. Subsequently Gemological Institute of America (GIA) and American Gem Society (AGS) were established with the purpose of training individuals in the art of appraising gems and precious stones. At present, a number of professional associations around the world provide certification and graduate diploma programs for gemologists.
Some of the popular gem Institutes and societies include:
• American Gem Society - AGS
• Gemological Institute of America - GIA
• Gemmological Association of Great Britain - Gem-A
• Canadian Gemmological Association - CGA
• Canadian Institute of Gemmology - CIG
• International Gemological Institute - IGI
• International Gem Society – IGS
How Gems are Appraised and Identified in Gemology?
Gemstones are classified based on optical properties and physical properties. Some of the properties include structure, specific gravity, refractive index, color, scratch resistance, and others. Mohs scale is used to determine the scratch resistance or hardiness of the gems, which range from one to ten.
Gem identification is based on the process of elimination. Gemstones are put to non-destructive optical testing until they are properly identified. Generally gemologists use the following three processes to identify and appraise the gems.
• Identification by Specific Gravity
A gem is identified through Specific gravity by comparing the weight of the gem suspended in water to its weight in air. Gemologists use heavy liquids of known specific gravity to appraise the gemstones. The specific gravity of gems differs and depends upon the structure of the crystals and chemical composition.
• Identification by Refractive Index
Another test to appraise and identify the gem is through refractive index method. Through this method, gemologists determine the gem by measuring refraction of light in it. Different gems have critical angles at which point is internally reflected back in the gem. Normally, a refractometer is used to measure the refractive index but a microscope can also be used for this purpose.
• Identification by Spectroscopy
Spectroscopy is the study of interaction between matter and radiated energy. Gemologists employ gemological spectroscope to analyze the selective absorption of light by the gem. The process is similar to using a prism to separate light into its constituent colors. Gems are identified based on how much light is bent when it passes through the gems. Chromophores or coloring agents display bands in the spectroscope that helps in identifying the gem.
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