FINENESS (KARAT VALUE)
Since ancient times the purity of gold has been defined by the term karat,which is 1/24 part of pure gold by weight. Pure gold is equivalent to 24K. Gold purity may also be described by its fineness, which is the amount of pure gold in parts per 1000. For example, a gold ring containing 583 fine gold has 583 parts (58.3%) gold and 417 parts (41.7%) of other base metals.
Federal Trade Commission rules require that all jewelry items sold in the United States as gold shall be described by "a correct designation of the karat fineness of the alloy." No jewelry item less than 10K may be sold in the United States as gold jewelry.
Karat Value Definitions:
- Karat System: A system of measurement based on 24 karats being "fine" or "pure" gold. 1 karat equals 1/24th fine gold by weight. This is the system used in the United States.
- Plumb Gold: Karat weights are usually determined with a small, fractional variance allowed. Karat gold which has no variance and is exactly the precise fractional karat weight is called "plumb" gold.
- European System: A system of measurement based on a fraction of 1,000; or the number of grams of gold in 1 kilogram of alloy.
The following table lists the relationship between different international gold markings.
GOLD KARAT INFORMATION CHART
|Karat Gold||Parts Gold||Percentage Gold||Normal European Stamping|
|9 kt||9 in 24||37.50%||375|
|10 kt||10 in 24||41.67%||416|
|12 kt||12 in 24||50%||500|
|14 kt||14 in 24||58.33%||583 or 585|
|18 kt||18 in 24||75%||750|
|22 kt||22 in 24||91.67%||917|
|24 kt||24 in 24||99.99%||999 or .99999|
WEIGHING PRECIOUS METALS
The weight of a piece of gold jewelry is a factor that helps to determine its value. It is important because it is an indication of the amount of fine gold in an item of jewelry. Grams (g) and pennyweights (dwt) are the units of weight most commonly used in weighing gold. Gold and silver are almost always weighted in the troy system of weights where one pound troy equals twelve troy ounces and twenty pennyweights equals one troy ounce. The Avoirdupois weight system, where one pound equals 16 ounces, is used in the United States for most everything except precious metals. The following table summarizes useful weight conversions.
|1 gram (g)||= 0.643 dwt = 0.0032 oz t = 0.035 oz av|
|1 pennyweight (dwt)||= 1.555 g = 0.05 oz t = 0.055 oz av|
|1 troy ounce (oz t)||= 31.103 g = 20 dwt = 1.097 oz av|
|1 ounce avoirdupois (oz av)||
= 28.3495 g = 18.229 dwt = 0.911 oz t