While modern gold coins are also legal tender, they are not observed in everyday financial transactions, as the metal value normally exceeds the nominal value. For example, the American Gold Eagle, given a denomination of 10 USD, has a metal value of more than $800 USD (being around a half an ounce). - wiki
(There is, of course, also the case of certain low-denomination coins costing more to manufacture than their face value - we're talking pennies and nickels, here - but that is a separate issue, and governments have taken measures to correct that.)
Again: Pardon!
Regards,