When you turn virtual currency into anything real (including US$, gold coins or something else) you have to deal with the capital gains implications.
The sales price of the virtual currency is the daily cash exchange price of the virtual currency. Then, you have to look at the purchase price for the same currency. If you sell for more than you paid, you have a capital gains transaction and owe either short term capital gains tax (held one year or less) or long term capital gains tax (if the virtual currency was held more than one year.) This is reported on schedule D under income from sales of assets. Since you do not get a 1099-B from the exchange, like stockbrokers issue for other investments, you need to keep excellent records documenting the purchase price and sales price of each coin or part of a coin that you buy so you can determine you gain accurately. If you are audited and your records aren't adequate, the IRS can determine that the entire proceeds is gain.
Then, you have now bought another asset with the proceeds, in your example, gold coins. You need to keep track of the purchase price. When you eventually sell them, you have a capital gain or loss at the time of sale, if you sell for more or less than the purchase price.
