What Is A Karat?
Everyone has come across the term Karat, in relation to gold or gold alloys. And we all know the higher the number of karats, the purer the metal. But how exactly does the system work?
First of all, we need to get the spelling correct. In the US and Canada the word is spelled karat while the rest of the world spells it carat. The abbreviations are kt and ct respectively.
Karats are a measure of the purity of gold. It is based on a system of 24ths. That is 24 karat gold is the purest gold possible (99.9% pure). 18 Karat gold is 18/24 (or 75%) pure and 12 Karat is 12/24 or ½ or 50% pure and so on.
Historically, for greater accuracy in measuring the purity of the metal, a karat could be divided into four “grains” and each grain, in turn, could be divided into four “quarts.” For example, gold that is between 18 and 19 karats in purity could have been described as being 18 karats, 2 grains and 2 quarts (18.5 karats). Today these finer measurements are no longer in use.
Karats are increasingly being replaced by the millesimal fineness measurement which allows for greater accuracy. Millesimal fineness is a system of rating the purity of precious metals by denoting the quantity in an alloy in terms of parts per thousand. For example an alloy that is 90% gold will have a millesimal fineness of 900. The millesimal number is usually rounded off to three digits and fractional measurements are not used.
The word karat has an interesting origin. It is derived from the Greek word Keration or “fruit of the carob” – an evergreen shrub. Carob seeds were thought to be uniform in weight and were used on precision scales to weight diamonds and precious metals.
In the US, the Fair Trade Commission has standardized the use of karat markings on gold. All gold items made of 10 karat gold or higher levels of purity must carry a stamp of either “K” or Kt.” Infractions of this law can have serious consequences including large fines.
Leave a Comment
If you would like to make a comment, please fill out the form below.
Recent Comments