Micronesia is an archipelago nation, far and isolated in the Pacific Ocean. The Yap islands group is part of Micronesia and has a very peculiar currency: stone. Stone money known as “Rai” are large stone disks, sometimes measuring up to 4 meters, with a hole in the middle that was used for carrying them. It was and still is used as a trading currency there. Interestingly enough, most of the stones have not been mined on Yap but on the neighboring island of Palau. The Yapese would take the ocean on their canoes and rafts and sail all the way there. They would quarry the stones and then bring them back home. In exchange for letting them mine the stones, the inhabitants of Palau would get copra, coconut or beads. The danger and time it took to bring back the stones were part of their value, as well as their size and age. The larger and the more ancient, the more value a stone has. Because the rais are not mined anymore, their value is now fixed.
If you hike through the island, you will easily notice the rais that are often placed by the side of the trail. Some of them are so heavy they cannot be moved easily so when they are being traded, ownership is passed orally between the two parties. There are no other records than the words of men.
Even though the US dollar is now the official currency in Micronesia, stone money is still used for important transactions such as marriage, purchase of land or compensation in case of wrongdoing.