A 12-year-old boy from North Carolina found a 5.16 carat diamond at the Arkansas' Crater of Diamonds State Park.
Michael Dettlaff, who visited the park in July along with his family, described the diamond as something that "didn't look like anything else around it," according to a report in ABC News.
According to the Associated Press, Michael's discovery is the 27th largest diamond found in the park so far by its visitors, ever since it became a state park in 1972.
"What they tell you you're going to find is these little diamonds [that are] so small," Michael said. "I kind of expected to maybe get a couple of those.
"We were probably there about 10 minutes and I was looking around on the ground and found it on top," he said. "It was very glassy. Very smooth."
According to the Park's Web site, it is the only diamond-producing site which lets public search for diamonds and also lets them keep it, no matter how valuable the stone discovered by them is.
"Any diamonds, semi-precious stones, rocks, or minerals you unearth are yours to keep, regardless of their value," the website states.
Michael's family did not realise the value of what he had found until Michael and his sister took the jewel to the park's free identification center.
"Later on in the day, right when we were ready to quit, my wife showed it to me again and then I thought, you know, that might really be something," Michael's father Chris Dettlaff said.
"We let the kids go up to the rock identification people by themselves and all of a sudden it's like this five-carat diamond. It was just crazy after that," he added.
According to the AP report, the honeyish-brown diamond is the eighth-largest brown diamond to have been certified by park staff.
Michael's diamond, which he has named "God's Glory diamond," could fetch him about $15000 after its cleaning and shaping.
"If it can get cut and it's valuable, I think I'd probably want to have it cut and sell it," Michael said. "If it's not, well, then it's a souvenir."