"As my eyes were panning to it, I was thinking it could be an amber piece of glass like an old Coke bottle," McCool said. "Once I focused on it though, I knew it was a diamond. I was like 'No way! No way!'"
McCool took his discovery to the diamond identification table, where his suspicions were proved correct.
"Mr. McCool's find is a 4.49-carat sparkling, canary yellow diamond that is about the size of a jellybean and seems to have great clarity. It is a stunning diamond," Crater of Diamonds State Park Assistant Superintendent Meghan Moore said.
Officials said it was the third-largest discovery so far this year.
McCool dubbed his discovery the BamMam Diamond, in honor of his children's initials.
"What's more precious than a precious gem? My children. So, I named it after my children and the name will stay with the diamond forever," he said.
"I called my son afterward and asked him if he remembered what Thanos' Mind Stone looked like, and told him I found one!"