Exquisite Emerald

by AMNH on

From the Collections posts

Measuring just over 2.5 inches tall, the Patricia Emerald is among the world’s most magnificent uncut emeralds. 

This gem is a rare uncut emerald crystal.
The Patricia Emerald is among the world’s most magnificent uncut emeralds.
© AMNH/J. Beckett

The 632-carat crystal group weighs about 4.4 ounces, and is the largest example recovered from the Chivor Mine in Colombia, one of the world’s most renowned emerald-producing countries. Because of their value, most emerald crystals of comparable size have been cut into gems and sold commercially. “Only a small number of large emeralds have been saved, and we are indeed lucky to have one of the fabulous few,” says George Harlow, curator in the Department of Earth and Planetary Sciences

Colombian emeralds are valued the world over for their superb color and relative clarity. The high quality of gems is due to the unique process by which the crystals take shape. While emeralds from deposits in North Carolina and Russia occur in metamorphic rock, Colombian emeralds are formed in fissures in sedimentary rocks like limestone and black shale. When hot, briny water passes over rocks and clays that contain chromium and beryllium, these elements are carried off in the flow, eventually coming together to form emerald crystals. Since they don’t form inside a rock containing other minerals, they have fewer inclusions, resulting in more transparent gems.

Historical sources say that the Patricia Emerald was part of a pocket that featured an even larger crystal. Unfortunately, miners attempted to extract the stones from the surrounding rock using TNT, and the resulting explosion blew the larger stone to smithereens. Somehow, the Patricia Emerald survived the blast intact.

As for its distinctive moniker, it's thought that the Patricia Emerald was named after the daughter of an owner of the Chivor Mine. Just who that owner was, though, is unclear: a German owner, numerous American investors, and a Canadian corporation all held rights to the mine around this time.

A version of this story originally appeared in the Summer 2016 issue of the Member magazine Rotunda.