Provenance is very important when valuing emeralds. The origin of an emerald establishes a base value from which to start the valuation. For example, Colombia is famous for producing some of the world’s most beautiful and valuable emeralds. One of the most expensive emeralds, the Rockefeller Emerald was purchased by Harry Winston for 5.5 million dollars or $305,000 per carat in 2017 at Christies New York Auction. Provenance can be determined by studying the internal qualities of the emerald under a microscope and using other gemological tools such as light filters and laboratory equipment. To establish the true value of a fine emerald, a gemological laboratory should be consulted and a grading report provided. Most very fine emeralds are accompanied by gemological reports from two different laboratories.