A rai stone (Yapese: raay),[1] or fei stone,[2] is one of many large artifacts that were manufactured and treasured by the native inhabitants of the Yap islands in Micronesia. They are also known as Yapese stone money or similar names.

A large (approximately 8 feet in height) example of Yapese stone (Rai) in the village of Gachpar

The typical rai stone is carved out of crystalline limestone and is shaped as a disk with a hole in the center. The smallest may be 3.5 centimetres (1.4 in) in diameter. The largest extant stone is located on Rumung island, near the Riy village; it is 3.6 metres (12 ft) in diameter and 50 centimetres (20 in) thick, and weighs 4,000 kilograms (8,800 lb).[3][4]

Rai stones were quarried on several of the Micronesian islands, mainly Palau,[5] but briefly on Guam as well. The practice stopped in the early 20th century. Today there are around 6,000 large rai stones outstanding in the island,[clarification needed] and several can be seen in museums around the world.[6][7]

The stones were highly valued by the Yapese, and used for important ceremonial gifts. The ownership of a large stone, which would be too difficult to move, was established by its history as recorded in oral tradition, rather than by its location. Appending a transfer to the oral history of the stone thus effected a change of ownership.[3]

Rai stones have been viewed by modern economists as a form of money, and are often used as an example to support the thesis that the value of some form of money can be assigned purely through shared belief in said value.[3][8]

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