The plain and simple definition of “karat” is “a unit for measuring how pure a piece of gold is. The purer the gold, the softer it is. This creates a bit of a conundrum because, as we know, people make jewelry out of gold, and the gold will essentially lose itself because of regular handling. The solution? Make it an alloy. In other words, pure gold is mixed with different metals to make it sturdier, and consequently affects the karat.
I Still Don’t Get Where The Numbers Come From…
The karat value basically gives the percentage of pure gold when you divide by 24. The number 24 is the magic number. 24KT is pure gold, and you pretty much only see it in gold bars. It is too soft to use for jewelry or coins.
The highest karat value you will usually see is 22KT. If you want to know how much of that is pure gold and how much is another metal, divide 22 by 24. This will give you a decimal value. Move the decimal point two places to the right, and you get your percentage of pure gold, which in the case of 22KT gold is 91.6%. Most jewelry will be 18KT (75% pure gold) or 14KT (58%).
So, If It’s Not Pure Gold, What Is It?
Well, it depends. Gold can be combined with copper or silver to make it stronger, and sometimes a combination of the two. Occasionally, zinc will be added to counteract the effect copper has on the color of the gold (making it more rose-colored than yellow).
When it is stronger, it can also hold gemstones…18KT gold is ideal. Anything of a higher karat would be too soft. A downside of less pure gold has to do with tarnish. Now, pure gold will not tarnish, but the other metals will, so take care of your jewelry!