Indeed. In fact it's really not any different from using precious metals as currency, or backing up a currency with precious metals, since precious metals only have value because we like shiny things (yes I realize that some of them are valuable because they are actually useful). But if we valued materials based on how useful they were, we'd want to have our money backed up by Aluminum or Iron. It is our irrational desire for gold, silver and copper trinkets that gives those metals superior value to materials that have a common, regular usage (like Copper, Aluminum, Iron, or Oil). If people did not want for Diamonds because they are shiny, they would be worthless (they actually are...but I digress); as would gold and silver as their practical purposes are few.