She thought she had just picked up a piece of glass. Little did she know she had just unearthed the “find of a lifetime.”

A 71-year-old woman from Colorado was visiting Arkansas’ Crater of Diamonds State Park with her husband, son, and three grandchildren when she found a clear, white gem. Thinking it was a piece of glass she asked her son to put it in his pocket and continued surveying eroded ancient diamond-bearing volcanic crater with her family in search of the park’s famous natural diamonds.

“I was using a rock to scrape the dirt but don’t know if I uncovered the diamond with it or not. It was just lying on the surface,” she said in a statement. 

Upon returning to the visitor’s center the woman, who chose to remain anonymous, was told she had found a 2.63-carat white diamond – the largest gem found at the park this year.

“I didn’t know what to think,” she said. “I was shocked!”

The park, which is known for its all-you-can-pick diamonds, says 256 gems have been registered so far in 2018, five of which weighed at least 1 carat each – the average size of an engagement ring diamond in the US. That puts this nearly 3-carat diamond into context.

Around 20 percent of diamonds registered by the park are found on top of the ground, said a park spokesman. Periodically, staff plows the 37.5-acre diamond survey area to loosen the soil and help natural erosion along. As the park notes, diamonds are heavy for their size and, because they lack electricity, dirt often doesn’t stick to them. Furthermore, rainfall will help to uncover larger diamonds because it washes away the dirt and when the sun comes out, helps them sparkle for visitors to see.

“Like other rocks and minerals, no two diamonds are exactly alike. This white diamond is about the size of a pinto bean and is shaped somewhat like a fingernail. Several brownish, freckle-like marks along the surface give the gem a unique, one-of-a-kind appearance,” described Park Interpreter Waymon Cox.

Diamonds come in many shapes and sizes, but the park most commonly registers white, brown, and yellow. More than 75,000 diamonds have been found here since the first one was discovered more than a century ago. During a 1924 mining operation, a man named “Uncle Sam” reportedly discovered the largest ever found in the US – a white diamond with a pink cast rocking in at 40.23 carats.