The Federal Trade Commission is the U.S. consumer's protection
against fraud in jewelry appraisal, identification and grading
standards. The agency works diligently with the jewelry industry
to unravel the mystery of understanding the stamped hallmarks
that guarantee the purity of metal used by jewelers.
2) What is a Karat?
The purity of gold is measured in karats, which are expressed in
units of 24ths. Thus, pure gold is 24-karat or 100 percent gold,
18-karat is 75 percent gold, 14-karat is 58.5 percent gold,
and so on.
Gold jewelry is priced according to its purity, or karat weight.
A karat, or carat, is 1/24th part of pure gold. This pure gold
is commonly alloyed with other metals in increase its hardness and
decrease its cost.
In other words:
- 10K gold should be priced much less than 18K gold.
(The lower the karat the less expensive - unless fancy design.)
- 24K gold is rather soft and needs extra care to avoid
damage. It is pure gold (occassionally marked "pg").
3) What Types of Gold are there?
There is no such thing as naturally occurring rose, white or
green gold. Gold itself is only one color: yellow. All of
other "colors" are a mixture of pure 24K yellow gold with
various other metals. The percentage of the other metals
(copper, silver, zinc, nickel) produces the different shades
of gold. Any karat other than 24K gold (pure gold) is called
24k gold by definition will always be "Yellow Gold" as it
is pure gold. However, one can still maintain a color close
to this yellow while adding other metals to create 10K, 14K
and 18K yellow gold. These alloys will be more durable than
the pure 24K gold.
Rose gold, known by other names such as pink gold or red gold,
is created by increasing the copper-colored alloys and
decreasing the silver-colored additives.
By increasing lighter alloys of silver, zinc, nickel and
copper tone down the yellow gold. The resulting 14K white
gold contains as much gold as 14K yellow gold but is nearly
white in color, though it still carries diminutive yellowish hint.
With its subtle, natural appearance, green gold is best showcased
in jewelry that combines yellow, white and pink gold. An alloy
of pure yellow gold and pure silver produce the green tint. For
durability, harder metals such as nickel or zinc can be used.
To create true 14K green gold, jewelers use 14 parts yellow
gold and ten parts silver. 18K green gold would contain
eighteen parts yellow gold and six parts silver.
Green gold can be hard to find.
taken from: http://www.jewelrymall.com/newsletters/050426.html March-25-2010