Fineness

Millesimal Fineness and Karat System

• Millesimal fineness is a system used to denote the purity of platinum, gold, and silver alloys.
• It is expressed in units of parts per 1,000.
• Many European countries use decimal hallmark stamps instead of karats.
• Millesimal fineness is an extension of the older karat system.
• Karat is a unit used only for gold and measures the parts per 24, with 24 karat gold being considered 100% gold.
• The minimum legal karat for gold in the US is 1 karat.
• Jewelry generally still uses the karat system for purity measurement.

Platinum Fineness

• Common purities for platinum include 99.95, 999, 950, 900, 850, and 750.

Gold Fineness

• Common purities for gold include 999.999, 999.99, 999.9, 999, and 995.
• 999.999 is the purest gold ever produced, while 999 is 24 karat gold.
• 995 is the minimum allowed purity for Good Delivery gold bars.

Silver Fineness

• Common purities for silver include 999.99, 999.9, 999, 980, and 958.
• 999.99 is the purest silver ever produced, while 999 is fine silver used in Good Delivery bullion bars and most current silver bullion coins.

Verifying Fineness and Fine Weight

• Two options for verifying the marked fineness of metal are assaying and using X-ray fluorescence (XRF).
• Assaying requires destroying the metal, while XRF measures only the outermost portion of the metal.
• Unscrupulous refiners may produce slightly less pure bars than marked.
• The fine weight refers to the weight of the precious component in an alloy metal and is used to determine the value and purity of the precious metal.

Fineness Data Sources