Yap stone money

Yap is one of the four states of the Federated States of Micronesia. A very interesting island and a fascinating history. Yap is especially known for its stone money, pictured here. The Wikipedia says:

Yap is notable for its stone money, known as Rai: large doughnut-shaped, carved disks of (usually) calcite, up to 4 m in diameter (most are much smaller). The smallest can be as little as 3.5 centimetres in diameter . Many of them were brought from other islands, as far as New Guinea, but most came in ancient times from Palau. Their value is based on both the stone's size and its history. Historically the Yapese valued the disks because the material looks like quartz, and these were the shiniest objects around. Eventually the stones became legal tender and were even mandatory in some payments.

The stones' value was kept high due to the difficulty and hazards involved in obtaining them. To quarry the stones, Yapese adventurers had to sail to distant islands and deal with local inhabitants who were sometimes hostile. Once quarried, the disks had to be transported back to Yap on rafts towed behind wind-powered canoes. The scarcity of the disks, and the effort and peril required to get them, made them valuable to the Yapese. Approximately 6,800 of them are scattered around the island.

As no more disks are being produced or imported, this money supply is fixed. The islanders know who owns which piece but do not necessarily move them when ownership changes. Their size and weight (the largest ones require 20 adult men to carry) make them very difficult to move around. Although today the United States dollar is the currency used for everyday transactions in Yap, the stone disks are still used for more traditional or ceremonial exchange. The stone disks may change ownership during marriages, transfers of land title, or as compensation for damages suffered by an aggrieved party