Are diamonds found in the United States? 

The answer is yes! Diamonds have been found in the United States, all the way from North Carolina to California and from Georgia to Wisconsin.

Why are diamonds so desired? Diamonds are extremely rare and they are the hardest mineral on the Moh’s scale, making them very durable. But a lot of the diamond alure has to do with good marketing. The De Beers company founded, the world's largest diamond mining company, promoting diamonds as the must have in every engagement ring. For most of the 20th century over 80% of the world's rough diamonds passed through De Beers. That number decreased in the late 1990’s-early 2000’s during the blood diamond scandal. DeBeers sold off most of their stockpile. As of January 2011, De Beers states that it only sells diamonds from the following four countries: Botswana, Namibia, South Africa and Canada.

Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths between 93 and 155 miles in the Earth's mantle, although a few have come from as deep as 500 miles. Under high pressure and temperature, carbon-containing fluids dissolved various minerals and replaced them with diamonds. Much more recently (hundreds to tens of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites. Diamonds in the rough usually have a frosted look, with rounded crystal faces.

In the U.S., diamonds have been found in Arkansas, Colorado, New Mexico, Wyoming, and Montana. In the Appalachian region diamonds have been reported found in Virginia, West Virginia, North Carolina, Georgia, Alabama, Kentucky and Tennessee.

The Great Lakes region has the largest diamond fields found in the United States. These were carried down long ago by great glaciers that advanced and retreated from Canada. As the glaciers retreated, they left behind boulders, gravel and clay the ice had carried down. The diamonds were found at the outer limits these glaciers reached in Milwaukee, Wisconsin to Cincinnati, Ohio. Wisconsin diamonds have a characteristic dodecahedral shape, as opposed to the more common Africa ones that are octahedral in shape.

Most diamonds are found in the course of gold mining. North Carolina and Georgia are active gold mining states and lots of diamonds have been found there. A large number of diamonds have been found in the Brown and Morgan counties in Indiana, because gold panning has been done for years in the creeks there.

And of course, on the west coast a great many diamonds have been found. Diamonds were found in California during the gold rush. California diamonds are usually found in placer gravels, and black sands and concentrates, and mostly north and south of Sacramento.

In 2004, the discovery of a microscopic diamond in the U.S. led to the January 2008 bulk-sampling of kimberlite pipes in a remote part of Montana. The Wyoming Geological Survey believes that there are lots of diamonds still undiscovered in their state. Wyoming has comparable conditions to the Canadian diamond deposits, and hundreds of kimberlite pipes are believed to exist.

The largest alluvial diamond found in the U.S. is known as the Punch Jones Diamond. The 34.48 carat alluvial diamond was found in 1928 in Peterstown, West Virginia by members of the Jones family while playing horseshoes.

In early 1854 or in 1853 Benjamin Moore was digging into a clay hill at the corner of 9th and Perry streets in Manchester, Virginia when he pulled out an 18 3/4 carat diamond.

There have only been two areas in the Unites States where diamonds were mined commercially. The Kelsey Lake Diamond Mine near Fort Collins, Colorado produced small amounts of diamonds between 1996 and 2002, when the mine was closed due to legal problems. And a mine near Murfreesboro, Arkansas. It was worked as a commercial diamond mine by a succession of operators in the early 1900s but closed because the deposit was not prolific enough to be profitable.

That area is now known as the Crater of Diamonds State Park and it is the only mine in the world where people can pay to dig for diamonds. More than 35,000 diamonds have been found by park visitors since the Crater of Diamonds became an Arkansas state park in 1972.

The Herkimer Diamonds found in western New York are not genuine diamonds, they are double-terminated quartz crystals that form in vugs of the Little Falls Dolostone.