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Technical Data for Gold

Ever wondered what the difference was between gold plating and gold filling? Or how about 23 karats of gold and 10 karats? Read on.

  • Gold is a yellow, noble metal.
  • Its chemical symbol is Au, from Aurora or dawn.
  • The weight of gold or gold articles is usually expressed in troy ounces. (1 troy ounce = 1.097 ordinary ounces)
  • The purity of gold articles is generally described in three ways: percent (parts of gold per 100), fineness (parts of gold per 1000) and karats (parts of gold per 24).


Gold Coated
Many gold-coated aricles are also used as substitutes for solid karat gold. The thickness of the coatings are often expressed in millionths of an inch, or microinches, and the table below provides a way to translate between these and other measurement units.

 

 

Thickness Equivalents
1 millionth inch (microinch)
=
.0254 micron
1 thousanth inch (mil)
=
25.4 microns
1 millionth meter (micron)
=
39.37 microinches
1 millimeter
=
39.37 mils

Following are the definitions of various gold-coated articles which are sometimes used in place of solid karat gold.

Gold Filled: also called gold overlay, a layer of at least 10-karat gold permanenetly bonded by heat and pressure to one of more surfaces of a supporting metal, then rolled or drawn to a prescribed thickness. The karat gold must be at least 1/20 by weight of the total meta content.

Rolled Gold Plate: Material consisting of a layer of plating of 10-karat gold or better which is mechanically bonded to a base metal. The karat gold content may be less than 1/20 but must be properly identified by weight in terms of total metal content.

Gold Electroplate: A coating of at least 10-karat gold or gold alloy plated on a base metal by electrolysis. The gold plating must be at least seven-millionths of an inch thick. Electroplating is widely used in the electronics and aerospace industries.

Gold Wash or Gold Flash: A film of gold less than seven-millionths of an inch thick, electroplated on a base metal.

Vermeil: Sterling silver coated or plated on all significant surfaces with gold or gold alloy of not less than 10-karat fineness.

Purity
The purity of gold articles may be described in three ways:

Percent, meaning parts of gold per 100
Fineness, meaning parts of gold per 1,000
Karat, meaning parts of gold per 24. Not to be confused with the carat, equaling a fifth of a gram, which is used to state the weight of a gem stone. The following table shows the examples of these value for some common grades of gold.


Percent Gold European System Karat System
100%
=
1000 fine
=
24 karat
91.7%
=
917 fine
=
22 karat
75.0%
=
750 fine
=
18 karat
58.3%
=
583 fine
=
14 karat
41.6%
=
416 fine
=
10 karat*
*The minimum amount of gold that a product can be composed of and carry the label "gold", according to the U.S. Federal Trade Commission "Guides to the Jewelry Industry."

 

Weight

The weight of gold or gold articles is usually expressed in troy ounces. The table below provides a convenient way to translate between troy ounces and other units of weight.

Weight Equivalents
1 troy ounce =
20 pennyweight
1 troy ounce =
1.097 ordinary ounces
1 troy ounce =
480 grains
1 troy ounce =
31.1 grams
1000 troy ounces =
31.1 kilograms
1 gram =
.03215 troy ounces
1 kilogram =
32.15 troy ounces
1 tonne =
32,151 troy ounces
1 avoirdupois (ordinary) ounce =
.911 troy ounces
1 avoirdupois (ordinary) pound =
14.58 troy ounces



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