24 Karat. .999, Fine and pure gold is what is called a noble metal. Noble means that it won't oxidize when exposed to the atmosphere and other agents which would rust steel and oxidize or turn silver black. Pure gold is generally considered too soft for jewelry use and to toughen it up for daily wear it is alloyed with other metals using the Karat system.
The Karat system has 24 parts and works like this: 14 Karat gold is made from 14 parts pure (24K) gold and 10 parts alloy. (14 + 10 = 24) 18 Karat gold is composed of 18 parts 24K gold and 6 parts alloy. (18 + 6 = 24 ) The mix always adds up to a total of 24 parts. Thus to figure what percentage of 24K gold an item is you simply divide the Karat marked on the piece by 24.
- 10K / 24K = .4166 or 41.66% gold with the balance being alloy metals
- 14K / 24K = .5833 or 58.33% gold with the balance being alloy metals
- 18K / 24K = .7500 or 75.00% gold with the balance being alloy metals
In the US, the lowest legal gold content allowed for manufacturing and sale to the public is 10Karat. 14Karat is the most widely used in the jewelry business. It has good working and wearing properties and it has a brighter yellow color than 10Karat which tends to darken with wear. In Europe, 8 & 9 Karat gold is allowed for sale and is usually marked .333 or .375.
What is White gold or Red and Green gold like we see in "Black Hills " jewelry? For example, yellow gold is alloyed with copper, silver and zinc with trace elements added for different colors of yellow. Colored golds have the same Karat content of gold as yellow gold does. When white gold is made, only white metals are used for the alloy mix such as silver, nickel and zinc with trace amounts of other white metals for color or certain working properties. Red gold has more copper in the mix which gives it the reddish color. Green gold is mixed with silver a bit of copper and other trace elements to impart the greenish color. Regardless of the color, if it is marked 14K, it must have 14 parts pure gold and 10 parts alloy mix in the recipe. The purity of Karat gold is mandated by federal law under the stamp act and plumb gold laws.
Recycling old gold is one of the most environmentally sound things you can do. Hundreds of thousands of tons of earth and rock must be moved, crushed and processed with acids, mercury and other chemicals to remove the gold produced by the average mining operation. For every ounce of gold that is recycled it saves the damage caused to the environment by excavating, crushing and processing hundreds of tons of mother earth! Gold plating is a waste as there is no practical method of reclaiming the gold lost to plating.
Did you know the planet's supply of gold would make a brick the size of a football field as tall as it is wide? Most of the gold mined over the history of civilization is at the bottom of the sea lying in shipwrecks. It is true that an ounce of gold can be drawn into a sheet so thin that light will pass through it. It is said that gold wire can be made so fine it would reach from New York to Los Angeles. A gold salt called Auric Chloride is used in the treatment of arthritis. Gold is used in dental work because it has similar wear properties to tooth enamel.