One of the largest U.S. diamonds was mined in Larimer County. Now it's at the Smithsonian.

Erin Udell, Fort Collins Coloradoan
·2 min read

From Northern Colorado to our nation's capital, a pair of Larimer County-mined diamonds have made quite the journey.

The Freedom Diamond and Colorado Diamond Crystal — both mined from the now-defunct Kelsey Lake Diamond Mine in Larimer County — are currently on display as part of The Smithsonian National Museum of Natural History new exhibit, "Great American Diamonds." 

The Kelsey Lake mine, which was actively mined from 1996 to 2001, was one of only two diamond mines to have operated in the United States, according to the Smithsonian. The other — Arkansas' Crater of Diamonds — produced the 40.23-carat Uncle Sam Diamond, the largest uncut American diamond ever discovered.

The Uncle Sam Diamond is also on display as part of the "Great American Diamonds" exhibit.

While it's not the largest uncut diamond found in the U.S., Larimer County's Freedom Diamond is the largest faceted diamond ever to originate in the country. The cushion-cut gem was fashioned from a 28-carat diamond crystal and is now set in a ring.

The Freedom Diamond, from the National Gem Collection at the Smithsonian Institution National Museum of Natural History, is pictured. The 16.87-carat, cushion-cut diamond in this ring was cut from a 28.18-carat diamond crystal mined from Kelsey Lake, Colorado in 1997. It is the largest faceted diamond from the United States.
The Freedom Diamond, from the National Gem Collection at the Smithsonian Institution National Museum of Natural History, is pictured. The 16.87-carat, cushion-cut diamond in this ring was cut from a 28.18-carat diamond crystal mined from Kelsey Lake, Colorado in 1997. It is the largest faceted diamond from the United States.

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Larimer County's history of diamond mining began in 1964, when Colorado State University professor Malcom McCallum discovered deposits of kimberlite — an igneous rock that sometimes contains diamonds — near the Colorado-Wyoming border.

More than a decade later, in 1976, McCallum and others found their first diamonds there, according to Coloradoan archives.

The Kelsey Lake site was prospected in the early 1990s, and in June 1994, a 14.2-carat gem diamond — then the sixth-largest ever found in North America — was mined there, according to Coloradoan reports from that time.

A few years later, the Freedom Diamond was mined — cementing itself in U.S. history. Despite these discoveries, the mine never saw commercial success and closed in 2001. It has since been reclaimed.

Both the Freedom and Uncle Sam diamonds were donated to the Smithsonian's national collection within a month of each other, allowing for the creation of the "Great American Diamonds" exhibit, according to the museum.

The Freedom Diamond and an uncut diamond crystal from the National Gem and Mineral Collection at the Smithsonian Institution National Museum of Natural History are pictured. Both of these diamonds, among the largest and finest diamonds found in the United States, originated from Kelsey Lake, Colorado, one of only two locations in the United States where diamonds have been mined.

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Erin Udell reports on news, culture, history and more for the Coloradoan. Contact her at ErinUdell@coloradoan.com. The only way she can keep doing what she does is with your support. If you subscribe, thank you. If not, sign up for a digital subscription to the Coloradoan today. 

This article originally appeared on Fort Collins Coloradoan: Larimer County-mined diamond finds new home at the Smithsonian