"However, gold has the desirable characteristics that we all want the means of payment to have. Primarily, it is stable in monetary value. It has other desirable characteristics as well, such as being easy to store, infinitely divisable, a chemical element, compact and of high value, and so forth. This is why we say that “gold is money,” and it is why gold has so often been the foundation for successful monetary systems for the last five hundred years." Nathan Lewis

http://www.forbes.com/sites/nathanlewis/2011/12/01/returning-to-the-basics-what-is-money/