Tana discovered the gem at Arkansas' Crater of Diamonds State Park. She says she was digging in the dirt for about two hours when she found it on the surface.
The yellow, teardrop-shaped diamond is about the size of a jellybean.
Park officials say Tana has named her gem "God's Jewel."
The park is the only diamond-producing site in the U.S. open to the public.
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