While gold is a physical commodity...I assume you are making this comparison because the value of gold is used as some sort of standard of investment and you are trying to compare how scarcity can affect value...that would be relevant if the amount gold that actually exists(mined/processed) exceeded the amount sold on the market. Currently the "ownership" of gold(including silver and a few other commodities) meaning someone has purchased interest in gold held by a 3rd party, exceeds the actual amount of gold that has been mined, ever.
Most countries have rules regarding the amount of gold you can physically possess(ex. order 6102, and the like), there is little recourse for someone to see "their" gold. So, while gold's value could be related to actual scarcity theres no way to prove the amount of gold being "held" is not the same gold someone else has purchased interest in. At this point of obscurity and public ignorance gold might as well be bitcoins ...excuse me while I go start a gold exchange...when are the suckers born again?
Gold may be gold, but we don't actually sell gold do we?(yes I know there's a gold bullion vending machine in Dubai, thats a novelty not an investment vehicle)