Fineness
Definition
Fineness is the purity of a precious metal expressed as a decimal fraction of the whole, such as .999 or .9167. It tells you what share of the item is pure metal rather than alloy.
Fineness is the modern, precise way to state how pure a bar or coin actually is.
Why it matters
Two coins of equal weight can hold different amounts of gold if their fineness differs. A .9999 bar is almost entirely gold, while a .9167 coin is about 91.67 percent gold and the rest alloy. Pricing, melt value, and resale all hinge on the actual pure-metal content, so fineness is central to any fair comparison.
In practice
Common bullion bars are .999 or .9999 fine. The American Gold Eagle is .9167 fine but still contains a full troy ounce of gold, with copper and silver added for durability. To find pure content, multiply gross weight by fineness.
Common confusion
Fineness is not the same as karat, though they describe the same idea. Karat is a 24-part scale, while fineness is a decimal. For example, 22-karat equals roughly .9167 fineness.