Kalel Langford was visiting Crater of Diamonds State Park in Murfreesboro when he found the rock by a stream on Saturday.
The 14-year-old was in town with his parents for a baseball tournament when he found the diamond, which has been registered as the seventh largest found in the park since it was established in 1972.
Kalel was walking near the East Drain, in the southern portion of the park's diamond search area, when he spotted the shiny, dark brown gem.
He said the diamond was 'just a few inches from a stream of water, with a bunch of other rocks that were about the same size', according to the park's statement.
Kalel's father, Craig Langford said the family had only been in the park for 'about 30 minutes when he found it'.
The family stopped by the Diamond Discovery Center to have their finds identified before leaving the park, and Kalel was shocked to learn he had found one of the biggest diamonds in the park's history.
He has named it 'Superman's Diamond' and plans to hang onto it. Park interpreter Waymon Cox describes the diamond as pinto-bean sized and similar in color to coffee.
'This diamond is a truly extraordinary find,' Cox said. Cox said conditions were ideal for Kalel to find his diamond.
'About an inch of rain fell on the plowed search area during the week. A heavy rain can uncover larger diamonds near the surface. Diamonds have a metallic-looking shine and are often easier to spot on top of the ground,' Cox noted.
The largest diamond ever discovered in the US was the Uncle Sam diamond that was unearthed on the land in 1924.
The 40.23 carat Uncle Sam diamond was cut twice, the second being a 12.42-carat gem that sold for $150,000 in 1971, which would equate to about $880,000 today.
The diamond is the largest registered at the Arkansas State Park since June 24, 2015, when Colorado resident Bobbie Oskarson found an 8.52-carat white diamond that she named the Esperanza.
The park said 97 diamonds have been registered at Crater of Diamonds State Park so far in 2017, weighing a total of 26.84 carats.
More than 75,000 diamonds have been unearthed at the Crater of Diamonds since the first diamonds were found here in 1906.
According to dailymail.co.uk