What is a “troy ounce”?

A “troy ounce” is the standard measurement used for precious metals. It consists of 31.1034768 grams. In the world of precious metals, the words “troy ounce” and “ounce” are interchangeable. Base metals, such as copper, are not measured in troy ounces; they’re measured in avoirdupois (“regular”) ounces. A regular ounce weighs approximately 28 grams.