Park officials said Saturday that Michael Dettlaff of Apex, N.C., found the honey brown diamond on July 31 after searching for less than 10 minutes. He named it God's Glory Diamond.
Park officials say the diamond is about the size of a jellybean and is the 328th diamond found this year.
More than 75,000 diamonds have been found at the site since the first discovery in 1906 by John Huddleston, the farmer who owned the land at the time.
The largest diamond ever discovered in the United States was unearthed at the site in 1924 and weighed 40.23 carats.