(IDEX Online) - A visitor to one of the world's only dig-your-own-diamond attractions has walked away with a 2.23-carat stone.Beatrice Watkins, 56, was sifting soil at the Crater of Diamonds State Park, Arkansas, USA, a former commercial mine turned visitor attraction that now admits amateur miners for $10-a-day.She unearthed the biggest diamond this year and is allowed to keep it under rules of the state-owned park."My daughter googled similar-looking stones and thought it might have been iron pyrite, so I stuck it in my sack and kept sifting," she told local media, after realizing it was in fact a brown diamond.Beatrice, from Mena, in Polk County, Arkansas, had been searching for just 30 minutes on a family trip when she found the stone.Diamonds were first discovered at the site in 1906 by a farmer who owned the 37-acre site, which lies over an eroded lamproite volcanic pipe. It was operated as a commercial diamond mine before becoming an Arkansas State Park in 1972.Over 75,000 diamonds have been unearthed there most notably the Uncle Sam, a 40.23-carat white diamond with a pink cast, which remains the largest diamond ever discovered in the United States. An average of two diamonds a day are discovered. The park admits 800 amateur diamond diggers a dayIn 1990 a visitor unearthed a colorless, internally-flawless 3.09-carat diamond which the park bought for $34,700. The largest diamond found by an amateur prospector is the Amarillo Starlight, a 16.37-carat white diamond discovered in 1975.Pics courtesy Arkansas State Parks