The official currency of Micronesia is the US dollar, but the island state of Yap uses an additional form of money: limestone discs, some of which weigh more than a car.
Centuries ago, Yapese explorers journeyed 280 miles west in bamboo canoes to the island of Palau, where they encountered limestone for the first time. After negotiations with the people of Palau, the Yapese established a quarry, using shell tools to carve disc-shaped stones they named “rai.”
The stones varied in diameter from a few inches to 12 feet, and weighed up to 8,000 pounds. A hole punched into the center of each disc allowed the explorers to carry the larger stones toward their bamboo canoes using poles. Maneuvering the rai into the boats, and keeping afloat during the long journey home, was a much more treacherous undertaking.
Back on Yap, rai became a sort of currency, exchanged as part of social customs such as marriages, political deals, and inheritances. The value of each rai depended on its size, but also on its provenance—if explorers died during the expedition to retrieve a stone, it acquired a higher value. A transaction did not require the physical exchange of a disc, merely the acknowledgement of a transfer of ownership. In fact, one of the rai stones in active circulation sits on the bottom of the Pacific Ocean, having tumbled from a canoe during a storm on the way back to Yap. Islanders agreed on its value after hearing the story of how it came to rest on the ocean floor.
Though its appearance differed from other forms of currency, rai was not immune to the issues of your average economy—such as inflation. During the 1870s, an Irish-American adventurer named David O'Keefe accompanied the Yapese to Palau, where he used imported tools to carve the limestone. His methods sped up the rai production process, with negative consequences: Yapese placed a lower value on his stones than on the discs carved with traditional shell tools, and the sudden abundance of rai brought down its overall worth.
The quarrying of rai stones ended at the beginning of the 19th century, but the Yapese still exchange discs to commemorate traditions. Many of the 6,500 remaining rai are displayed in rows at outdoor “banks”—jungle clearings and village centers. Theft is not a concern.
It's all about the money: