Gold & Gold Alloys Used in Jewelry
- 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
- 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.