See also the use of giant rocks as currency: * https://en.wikipedia.org/wiki/Rai_stones https://en.wikipedia.org/wiki/Rai_stones Generally anything can be use

See also the use of giant rocks as currency: * https://en.wikipedia.org/wiki/Rai_stones https://en.wikipedia.org/wiki/Rai_stones Generally anything can be used as money if people agree to it. There is nothing inherent in in gold/silver/shells/whatever that make them "money".