Gemology or gemmology is the science dealing with natural and artificial gems and gemstones. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems.
Rudimentary education in gemology for jewelers began in the nineteenth century, but the first qualifications were instigated after the National Association of Goldsmiths of Great Britain (NAG) set up a Gemmological Committee for this purpose in 1908. This committee matured into the Gemmological Association of Great Britain (also known as Gem-A), now an educational charity and accredited awarding body with its courses taught worldwide. The first US graduate of Gem-A's Diploma Course, in 1929, was Robert Shipley who later established both the Gemological Institute of America and the American Gem Society. There are now several professional schools and associations of gemologists and certification programs around the world.
The first gemological laboratory serving the jewellery trade was established in London in 1925, prompted by the influx of the newly developed 'cultured pearl' and advances in the synthesis of rubies and sapphires. There are now numerous Gem Labs around the world requiring ever-more-advanced equipment and experience to identify the new challenges - such as treatments to gems, new synthetics and other new materials.
Gemstones are basically categorized based on of their crystal structure, specific gravity, refractive index, and other optical properties, such as pleochroism. The physical property of "hardness" is defined by the non-linear Mohs scale of mineral hardness.
Gemologists study these factors while valuing or appraising cut and polished gemstones. Gemological microscopic study of the internal structure is used to determine whether a gem is synthetic or natural by revealing natural fluid inclusions, and included partially melted exogenous crystals to demonstrate evidence of heat treatment to enhance colour.
The spectroscopic analysis of cut gemstones also allows a gemologist to understand the atomic structure and identify its origin as it is a major factor in valuing a gemstone.
For example, a ruby from Burma will have definite internal and optical activity variance as compared to a Thai ruby.
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