When talking about diamonds, the four C's come to mind — Color, clarity, cut and carat...but another "C" word that you typically wouldn't think about is Colorado, which actually has a huge connection to the diamond industry.

Tweezers holding diamond, close-up
Jeffrey Hamilton

Although it's now closed, Kelsey Lake Mine, located about 45 miles away from Fort Collins, has left a sparkling impression in mining history. That's because, back in 1997, one of the largest diamonds in North America was unearthed right here in Larimer County.

During its active years, Kelsey Lake Mine was one of two commercial diamond mines in the United States. The Northern Colorado site was first put on the map in 1975, when Kimberlite was accidentally discovered there. This peaked the interest of miners, being that it can sometimes contain diamonds. While it took several years to get rockin,' continuous exploration eventually paid off, and after several sizable diamonds were found, the term Colorado Diamonds was coined. Ownership of the mine changed hands over the course of years to come, and it was in 1997 when the prominent mining company, Redaurum, uncovered what was considered to be the fifth largest stone ever found in the United States – a 28.3 carat yellow diamond that was sized down and sold at one point for $87,000. Mining operations at Kelsey Lake ultimately ceased in 2001, reportedly due to financial and legal problems.

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