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Diamonds • Precious Gemstones • Jewelry • Gemology

Gold & Gold Alloys Used in Jewelry

Gold (Au)
  • Purity or "fineness" is designated by karatage (K); 24 karat gold is pure gold.
  • 12 karat gold is 50% gold and 50% alloyed metal.
  • Gold will alloy with nearly all base metals. Different colors of gold are produced by alloying with different base metals. Common alloys are Nickel (Ni) and Copper (Cu)
  • Specific Gravity for pure gold is 19.3.
  • Gold purity can be tested with inexpensive devices that measure electrical conduction, or by the older method of gauging the extent of reaction with dilute acids.
  • U.S.F.T.C. Guidelines governing sales of gold and gold jewelry in this country state the following:
    • 1) Karatage has to be stamped on, with trademark.
    • 2) Terms "pure gold" and "solid gold" can only be used for 24 karat gold.
    • 3) Term "gold" can only be used if gold content is 10 K or better.
    • 4) Term "gold filled" applies only to items composed of a layer of gold pressed (not alloyed) onto a base metal where the weight of the gold comprises at least 1/20th of the total weight of the item. Fineness must be shown by stamp, e.g. "1/20 12 k G.F." means the gold layer is 12 karat gold and comprises 1/20th of the total weight of the item.
    • 5) Term "rolled gold plate" is the same, but gold comprises less than 1/20 of total weight; e.g. stamped "1/30 12 k G.P." means 1/30 of the metal weight is from 12 karat gold plate.
    • 6) "Gold electroplate" or "gold flash" or "gold washed" means a gold coating that is 10 k or better gold at least 0.000007 inches thick. A variant, "heavy gold electroplate" (H.G.E.P.) is at least 0.0001 inches thick.
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