Generally, you do not owe wholesaling B&O, retailing B&O or retail sales tax on your gross income from sales of precious metal bullion (gold bars, processed nuggets, etc.) and monetized bullion (coins, etc.). This applies even if you sell bullion for more than face value.
Precious metal bullion is any processed, smelted or refined precious metal valued on its content, not form (RCW 82.04.062).
Precious metals include
Monetized bullion is a coin or other form of money made from metal and used as an exchange medium under the laws of a government (RCW 82.04.062).
You owe retailing B&O tax, and you must collect and report sales tax on your sales of coins that cannot be used as money (i.e. an exchange medium under the laws of a government).
Sales of bullion that will be used to manufacture items such as jewelry or works of art are subject to wholesaling B&O tax if you receive a reseller permit. Retailing B&O tax and retail sales tax applies on such sales to consumers.
If you receive commissions from sales of precious metal bullion and monetized bullion paper currency, you owe service and other activities B&O tax (WAC 458-20-248).