The stone coin, in Yap North or South Yap, is a Yap-specific monetary system, described by Cora Lee C. Gilliland, and then by Gregory Mankiw, a professor at Harvard University. Yap stones are large round stones similar to grindstones, with a hole in the middle, and whose size can range from diameter. They are cut in a native material composed of aragonite and calcite. Listed, they are in number and only for large purchases. For the rest, we use US dollars.
This system prevents inflation because the amount of money is limited and the flight is almost impossible. Broken, these stones have no value in the eyes of the natives. The inhabitants of Yap, so as not to risk breaking them during a perilous journey, leave the heaviest in the same place and mentally note who the stone belongs to. Some sites with many stone coins are a tourist attraction.