Geographic Origin Determination of Emerald By GIA.

Also FYI,

For more than 4,000 years, emeralds have been among the most valuable of all jewels on Earth. Colombia, located on the continent of South America, is the country that mines and produces the most emeralds for the global market. When it comes to rich coloration, beauty and perfection, Columbia emeralds are one of the top choices in the world. 

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Also, an optical feature called Gota de Aceite is seen in some of the finest quality emeralds from the Muzo Mine in Colombia. Gota de Aceite is Spanish for “drop of oil” and is so named because it creates an “oil-like” softening or roiled appearance in the stone. This is extremely beneficial for emeralds because the effect tends to de-emphasize internal inclusions, which are naturally prevalent in all emeralds, and emphasize the glorious, green body color of the stone. Emeralds that possess this feature have become quite desirable over the years, similar to the popularity of the velvety effect.

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