Not only 1 diamond mine in United States

Kelsey Lake Diamond Mine usa united states of americaThere appears to have been another diamond mine in the USA but it is no longer operating.

The United States only has two locations that have been operated as commercial diamond mines. One was the Kelsey Lake Diamond Mine near Fort Collins, Colorado. It produced small amounts of diamonds between 1996 and 2002 when the mine was closed due to legal problems.
United States Diamond Mines and Mining

Wyoming Diamond Mines?

Not only that but Wyoming suggests that it is a likely place to be a producer of diamonds in the United States of America. The same article suggests:

The Wyoming Geological Survey believes that a billion-dollar diamond industry could develop in their state. Wyoming has comparable conditions to the Canadian deposits and hundreds of kimberlite pipes are believed to exist. Their website has maps showing the location of diamond-hosting intrusives, reported placer diamonds, kimberlite indicator mineral anomalies, lamproites and diamond stability indicator minerals.

Some points that communicate their optimism for a significant diamond industry in Wyoming:

* 40 diamond deposits in the State Line District
* 130,000 diamonds recovered from the State Line District
* several diamonds weighing more than 28 carats
* hundreds of kimberlitic indicator mineral anomalies
* Wyoming has the two largest kimberlite districts in the U.S.
* Wyoming has the largest lamproite field in North America
United States Diamond Mines and Mining