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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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