"I'll see people pick one up and just toss it," she said. "They don't see it."
Cape May diamonds are usually pebble-size, though in 1942, a 14-ounce stone was found. It's unclear when people started collecting the stones, which appear on the Jersey Shore and along the Delaware Bay. But locals say that Sunset Beach, where the Atlantic Ocean meets the bay, is where you'll find the mother lode.
In reality, the diamonds are quartz, made of silica dioxide, said Jane Uptegrove, a geologist for the New Jersey Geological and Water Survey, based in Trenton.
Where scientists score actual diamonds a "10" for their hardness, Cape May diamonds are a "7."
"The clear quartz crystals have eroded from rocks upstream, most likely from northern Pennsylvania or northern New Jersey," Uptegrove said. "Ancient and present-day rivers" have transported them downstream "and the wave action at the confluence of the Delaware Bay and Atlantic Ocean has rounded and smoothed the pebbles."
Ed Hawley, 59, of Keyport, has come to Cape May and collected stones for 30 years. The biomechanical engineer, who designs medical and surgical instruments, believes there's a silica crystal shelf off the coast that is continuously eroded by the surf.
"Everyone has their own theory," said Hawley, who keeps his finds in a jar at home. "Some people think they come down from the Delaware Water Gap, but I think that's a little bit of a stretch."
Bartolomeo, the jewelry designer, subscribes to the Water Gap theory, but thinks a long-ago nautical accident helped.
On June 8, 1926, the Atlantus, one of 12 experimental concrete ships built around the time of World War I, capsized off Sunset Beach while being readied for reuse in a ferry slip. It still can be seen from the shoreline.
Bartolomeo thinks the wreck creates a whirlpool that sucks in the quartz that comes down the bay.
"The ship doesn't create the stones, but it does bring them in," she said.
Sunset Beach isn't the place to wear sandals or build a sand castle. It's all stones, incredibly smooth and worn and weathered.
On a windy day this summer, about 50 people strolled the beach, staring downward. Dan McCauley, 55, from Lancaster, Pa., sat on ground searching for diamonds.
"I have a couple in my pocket. They're just kind of neat to find them," he said. "The last time we were down here with our kids, we found a shard of a plate from a shipwreck, so that was very cool."
Sunset Beach was private property until the 1970s, when much of it was sold to the state, according to the New Jersey Department of Environmental Protection. The owners kept the property where the shop, built in 1973, stands. They collect the stones in buckets, particularly after winter storms.
Bartolomeo and her staff turn them into bracelets, necklaces, and earrings. It takes three weeks to turn a rough stone into a diamond using a series of abrasive and fine and polish finishes, she says.
But Bartolomeo has a few special ones she's held onto for years.
"I've found a couple hearts," she said. "I found one when I first started working here, and I've kept it ever since."
Jeannette Bartolomeo talks about looking for Cape May diamonds at www.philly.com/capemay
Contact Dawn Fallik at firstname.lastname@example.org.
This article and its accompanying video were produced as part of the "View From the Beach" series, partly funded by the University of Delaware.