The purity of any precious metal or stone has been defined by the term Carat or Karat.
Pure gold is equivalent to 24 Karat (24K). Pure gold comes in yellow, but it can be produced in shades of rose, white, green, and even two-tone.
None of these additional colors are natural, and instead produced by mixing pure 24K yellow gold with various other metals. The percentage of the other metals (copper, silver, zinc, and nickel) produces the different shades of gold. 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.”
Rose gold is also known as pink gold or red gold, and is a mixture of pure yellow gold with a high percentage of copper. It has a very subtle and delicate color that may intensify somewhat with age due to a slight, but commonly regarded as attractive, tarnishing of the copper alloy. Rose gold is created by increasing the copper-colored alloys mixed with the gold, and decreasing the silver-colored alloys. 14K rose gold contains as much pure gold as 14K yellow gold but, because of the increased copper, is slightly pinker in color.
White gold is created by increasing the silver-colored alloys (zinc, silver, nickel) normally mixed with gold and decreasing the copper-colored alloys. 14K white gold contains as much gold as 14K yellow gold but is nearly white in color.
Green gold is created by mixing an alloy of pure yellow gold and pure silver. For rings, harder metals such as nickel or zinc are sometimes added to make the gold more durable. The green color, like rose gold, is very subtle and is most noticeable when it is used in a piece of jewelry next to areas of yellow, white, and pink gold.
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.
grams (g); pennyweight (dwt); troy ounce (oz t); ounce avoirdupois (oz av)