BAR HARBOR, Maine — If one rock was selected to represent Acadia National Park on Mount Desert Island, it would have to be pink granite. The rough, rosy stone is found throughout the park, from the pebbles at the bottom of Jordan Pond to the cobblestones of Seawall Beach to the top of Cadillac Mountain.

That’s why, years ago, the Willis family began creating fine jewelry from the pink stone, flecked with black and gray.

“So many of our summer customers want the local stone,” said Roger Willis of Willis’ Rock Shop, a fixture on Main Street in Bar Harbor since 1937.

Willis and his cousin Deanna “De-De” Willis are the third generation of their family to run the shop and craft fine jewelry out of local stone, as well as semiprecious gems such as tourmaline, amethyst, aquamarine, calcite and peridot.

MDI pink granite, tumbled smooth and polished until it shines, has been a top seller at the shop for decades. To many island visitors, the common igneous rock holds more value than any gem. It means taking a piece of the island home with them.

So this year, in celebration of Acadia National Park’s 100th anniversary, the Willis family has decided to offer their popular line of pink granite jewelry as “Acadia Centennial Merchandise.” Each piece will be engraved with “ANP16,” and the shop will donate 5 percent of sales to the nonprofit group Friends of Acadia to benefit the park.

It’s important to note that while the pink granite in the jewelry comes from MDI, it was not taken from Acadia National Park, where removing rocks is a federal offense.

“I have a lot of pink granite on my property actually,” said Roger Willis, 61, who lives in Bar Harbor with his wife, Cheryl Prostak Willis. “And a long piece of granite goes a long way.”

Willis’ Rock Shop is offering its traditional pink granite line in 14-karat gold, with earrings, pendants, bracelets and necklaces ranging in cost from $175 to $1,000. And for customers with lower budgets, the shop is working to produce less expensive pink granite beads with a silver core that range from $38 to $52 and fit on the popular slide bracelets such as the bracelets made by PANDORA and Trollbeads.

All pieces will be in true Willis style, with classic metalwork showcasing large chunks of smoothed, rounded and polished stone. The design of the jewelry, all crafted in the back of the shop, has changed little over the years as the shop has been passed from one generation to the next.

Willis’ Rock Shop was established in 1937 by Roger and De-De Willis’ grandparents, Malcolm and Thelma Willis. Both former teachers of Bangor High School, Malcolm and Thelma Willis moved to Bar Harbor in the 1930s and opened a yarn shop, rock shop and watch shop.

Of the two, Malcolm Willis was especially interested in rocks and became an avid collector, purchasing vast quantities of minerals, some valuable and rare, others beautiful but worth little. The family is still digging through the remains of that collection today, sorting through hundreds of dusty crates and burlap sacks stored in the shop’s basement.

“He got the fever bad,” Roger Willis said. “There are about 10,000 pounds of semiprecious gems and stones in the basement.”

A handyman, Malcolm Willis constructed a giant rock tumbler using the parts of an old Volkswagen Beetle, and he developed a custom blend of powders to polish the stones faster and smoother. Over the years, the Willis family refined this mixture, which is responsible for the high polish of their gems.

Willis jewelry — made from start to finish in the back rooms of the shop — quickly gained popularity on the island, mostly through word of mouth. The quality of the pieces became so revered that in 1955, the Bar Harbor Chamber of Commerce presented a traditional Willis bracelet to the first lady of the United States, Mamie Eisenhower, wife of President Dwight D. Eisenhower.

As Malcolm Willis grew older, the shop and the tradition of jewelry-making was bestowed upon his sons Weston and Clayton Willis, and their wives, Jean and Geraldine, respectively. In turn, they passed the tradition on to their children.

“I grew up cutting granite,” said Roger Willis. “As a teenager, I’d cut granite and agate into bookends for the shop.”

Willis wasn’t always sure he’d take over the shop. In fact, he went to college to become a social worker. He liked working with people and didn’t think he’d like working with his hands for a living. But when his father, Weston Willis, became ill, he made the decision to buckle down and learn the fine art of jewelry-making.

Roger Willis has been cutting stones for more than 40 years with a diamond-flecked blade. The high whine of the saw has slowly ruined his hearing, and the cold water that runs through the saw to reduce dust makes his hands ache. Sometimes he dislikes his work, but whether he knows it or not, it appears that he too has caught “rock fever.”

In the back room of the shop, colorful gems litter his goldsmithing desk. Most are on their way to becoming classic pieces of Willis jewelry, but some rocks are there because he simply can’t part with them.

A slice of watermelon tourmaline, its pattern resembling the shape of MDI, sits in his drawer.

“See how the pink is the land, and the green is the ocean?” Willis said.

He then held up a green rock the size of a softball, its blocky exterior a foggy green.

“This is an emerald,” he said. “I can’t bring myself to cut into it. It’s so beautiful the way it is.”

His wife shook her head at the remark, smiling. Hers is the face most customers see when they walk through the shop’s front door.

“People go by and think we’re just a touristy gift shop,” she said. “We really are a hidden gem.”

De-De Willis, daughter of Clayton Willis, also carries on the family tradition as a jewelry designer and goldsmith. And completing the jeweler team is the shops only non-family employee, Katie Dyer.

The shop’s customer base still grows mostly from word of mouth, Roger Willis said, and many of their most loyal customers own summer homes on the island.

“People living on estates on the beach bring in their bags of rocks from their beach, and we’ll make a custom piece for them [out of the rocks],” he said.

While the backroom of the shop is all about jewelry-making, the storefront is more diverse. Surrounding the glass jewelry cases is a variety of merchandise, small gifts that help keep the business alive. And lining the walls are shelves of rock specimens, from smoky quartz crystals to less familiar rocks such as the greenish-blue chrysocolla.

“We’re a rock shop first and foremost,” Willis said. “We like rocks.”

Willis’ Rock Shop is located at 69-73 Main Street in Bar Harbor.

Aislinn Sarnacki is a Maine outdoors writer and the author of three Maine hiking guidebooks including “Family Friendly Hikes in Maine.” Find her on Twitter and Facebook @1minhikegirl. You can also...