Home >> Science & Nature >> Rocks & Minerals

How To Calculate Fineness

Fineness represents the purity of precious metals. Typically, it refers to jewelry, coins, bars and anything else that can be considered a collectible or valuable item. Precious metals are typically combined with an alloy to aid in strengthening the object. There are two main ways to calculate the fineness of precious metals: the karat and the 1/1000 method. The 1/1000 method can be shown on a precious metal one of two ways: .900 or "900 thous." These are synonymous in their usage.

Instructions

- 1
  Read the label or mark that defines the fineness of the piece you want to calculate.
- 2
  Calculate the karat if there is number followed by a "k." Karats are measured in 1/24 with 24/24 being 100 percent. A gold necklace which is 12 karats would be measured as 12/24 or 50 percent gold.
- 3
  Calculate the percentage if there is a decimal point followed by three numbers, such as .900. Simply multiply the number by 100 to find how pure the item is. As an example, we will take a silver ring which is stamped as .900.
  100 x .900 = 90
  The ring is 90 percent silver.
  If the ring reads "900 thous" then simply do the following:
  900/10=90
  Again, the ring is 90 percent silver.

Rocks & Minerals