It’s my second day at the Tucson Gem Show and I’m standing in front of the Expo Center, examining the fossilized shell of the world’s largest giant killer clam. It’s gray-white and smooth, with a lip that’s curvy and meandering, like a piecrust with a crimped edge.

“Should I sit in the shell?” Volker Bassen asks. He is the shell’s owner, a tall Swedish man who does not, at first glance, appear as if he would fit inside a clam shell. He crawls under the protective rail that cordons off the exhibit from passersby, and gently lowers himself into the carapace.

“It’s very strong material,” he says, grinning.

For two weeks every winter, nearly 60,000 people descend upon Tucson for the world’s largest gem and mineral show. More than $100 million of gems and minerals are sold as geology professors, Pakistani vendors, Southwestern mystics, and high-class jewelers wander from exhibition to exhibition in the dry Arizona air. At the Gem Show, you can buy anything from rocks to crystals to the fossilized remains of a beaver jaw from the Pleistocene. Some of the show’s visitors seem like businesspeople at a trade convention, while others are more eccentric. During the first 30 minutes of my visit, I saw two different men walking wolves, on leash, through the courtyard of a hotel.

Polished pieces of clam shell that resemble pearls on display at the Tucson Gem Show
(Wiley Rogers)

This is Volker Bassen’s first year at the show, and he is here to sell clam shells. Bassen collects the shells in East Africa, where he lives, and auctions them off around the world to support a variety of nonprofit ventures back home. This shell, the biggest ever found, is a major attraction in Tucson, and he hopes it will help fund an ambitious, albeit curious, new project: a menstrual-cup factory.

Tucson’s first Gem Show was held in 1955, in an elementary-school gym. From there it moved to the county rodeo grounds, where it took place inside of a Quonset hut. By 1972, the show had expanded significantly, and it relocated to the Tucson Convention Center, where it is based today. While the convention center serves as the locus of the event, different satellite shows pop up throughout the city, in circus tents, expo halls, and warehouses. Many local hotels are commandeered by vendors, who hawk their wares from inside their rooms.

Gem wares for sale at the show
(Wiley Rogers)

Volker Bassen’s enormous shell is featured at JOGS, an exhibition that focuses on jewelry. Like many of the other vendors at the show, Bassen has traveled a long distance to be here. In Diani Beach, Kenya, he works as a scuba-diving instructor and giant-clam shell collector. But these two vocations are not as closely related as one would think. None of the clam shells that Bassen collects are discovered underwater. They are found on land, in limestone quarries, which are ancient coral reefs. This particular shell was given to Bassen as a gift, by a local Digo chief, to commemorate the birth of his son.

“It was such a beautiful present,” he said. “It’s just amazing.”

Also known as Tridacna Gigantea, these extinct giant clams are the predecessors of Tridacna Gigas, the world’s largest living clams, which can be found in and around the South China Sea. According to Bassen, Tridacna Gigantea became extinct 180,000 years ago, when a glacier cracked open and released a huge store of water. Sea levels rose to a point that the clams, which lived in symbiosis with an alga, were no longer able to access energy from the sun, and died out. This particular clam weighed approximately 800 pounds.

“You have to imagine,” Bassen says. “This clam was full of meat. Sixty or seventy kilos of meat.”

I ask him why the clams are referred to as “killers,” if they survived primarily via photosynthesis. He explains that the U.S. Navy gave the modern giant clams this moniker in the 1960s, in a diving manual, which included instructions for how to extricate yourself from a giant clam if it’s mouth ever closed on your leg. The clams do indeed close, on occasion, in order to protect themselves, but they do so slowly. Bassen tells me that it was highly unlikely that a clam would close fast enough to trap someone’s leg.

“It is possible,” he says. “But they move so slow, you’d have to be a real idiot.”

Most clams that Bassen acquires are first found by local miners. After a discovery is made, the miners call him, and he travels to the mine and pays them an entire year’s salary to purchase the shell. He then excavates the shell and proceeds to clean and polish it, a process that can take up to eight weeks. Once the shell has been prepared, Bassen sells it and donates a percentage of the funds to a non-governmental organization that he founded, the East African Whale Shark Trust—“the roof for all our activities,” as he calls it.

The activities he’s referring to are dizzying in scope and variety. The trust runs an orphanage, funds whale-shark research, treats children suffering from the Jiggers parasite, and produces paper made from elephant dung, which is, according to Bassen, very popular in China. The organization came under fire in 2013 when it proposed creating a 2,000 foot-long enclosure for whale sharks in the Indian Ocean. The idea was to allow tourists to dive and snorkel alongside the giant fish. Critics accused Bassen of needlessly enclosing the whale sharks while Bassen said he was helping to promote the conservation of the species by showcasing their beauty. The project stalled, but he says he still hopes to execute it sometime down the road.

Fossils of giant-clam teeth
(Wiley Rogers)

The funds raised from this particular giant clam shell, however, are going to an entirely different endeavor. As we talk, Bassen digs into his pocket and pulls out a bell-shaped silicone cap. “It is the holy grail of menstrual hygiene,” he says. “How many men do you know who walk around with a menstrual cup in their pocket?”

Bassen learned about menstrual cups several years ago, when he took over an orphanage in Okunda, a coastal city near his home in Diani Beach. The orphanage supported 68 children and all of them were sleeping on the floor because their mattresses were infested with bed bugs. The pastor who ran the orphanage had poured diesel and paraffin on the mattresses in attempts to kill the bed bugs, and as Bassen and employees of his charity toured the place, they noticed that not only were the mattresses soaked in chemicals, but all of them were ripped. One of Bassen’s staff suggested that perhaps the children were having nightmares. After speaking with the children, however, Bassen learned that the young girls had been using the chemical-soaked, bed-bug-infested material from the mattresses to stop the flow of their periods.

Researching menstrual hygiene online, Bassen decided that menstrual cups are superior to tampons in every sense. Over the course of a woman’s lifetime, she will use more than 11,000 tampons, many of which will end up in the ocean or in landfills, where they take hundreds of years to biodegrade. A menstrual cup, on the other hand, is reusable for years. Its manufacturing cost in Kenya is only 10 cents, Bassen says. A box of tampons, by comparison, retails for approximately $4 dollars—a steep cost considering that 43.4 percent of Kenyans earn less than $1.25 (USD) per day.

Bassen is convinced that corporate interests have prevented the menstrual cup from becoming more widely popular—selling a woman thousands of tampons is more lucrative than selling her a menstrual cup once or twice per decade, after all—so he wants Kenya to be at the forefront of change. A few years ago, he opened his own menstrual-cup factory in Ukunda. Now he has plans to expand, with the aim of creating more jobs and distributing the cups throughout East Africa.

In Tucson, he hopes the sale of his giant shell will help purchase a $48,000 machine for the facility. His other shells have sold well in the preceding days, garnering enough money to fund his orphanage for another year. Still, this shell, the pride of his collection, has yet to be purchased. As we talk, visitors file in and out of the expo center and a security guard stops by to check on the shell. The Gem Show will continue another week. There is plenty of time to find a buyer.

Several days later, I receive an email from Bassen. After a bidding war between three buyers on the last day of the show, the clam shell sold for $32,000. Bassen himself is in London, preparing to depart for Kenya. Whale-shark season has begun and he can’t wait to get home.