Gold and silver aren't traded on currency exchanges.....
Are you certain about that?
XAU, XAG, XPT, and XPD -- gold, silver, platinum and palladium. The only commodities with official currency designations. And gold and silver are almost always available wherever you get forex quotes (XAU/USD, XAG/USG).
Tony Fell, Chairman Capital Markets, Royal Bank of Canada said in Feb 2007, "At Royal Bank of Canada, we trade gold bullion off our foreign exchange desks rather than our commodity desks, because that's what it is -- a global currency, the only one that is freely tradable and unencumbered by vast quantities of sovereign debt and prior obligations."