Gold is a relatively soft metal, and is therefore rarely used in its purest form to make things such as jewelry. Instead, to strengthen these items, other metals are added to the gold. This is called Karat Gold, and therefore, any gold that is not pure gold is considered Karat Gold.
To measure a gold karat, we must first understand that we measure gold purity on a scale of 24. 24 karat gold is *100% gold, or pure gold.
Think of it like this: Gold is broken down into 24 parts (by weight), and the content in gold karats would be represented by the number of “parts” of pure gold. For instance, if gold had 18 parts gold, it would be considered 18 karat gold or 18k gold. Note that 18 karat gold contains 6 parts of other metals. 24 karat gold does not have anything else added, so it is pure gold.
*Note: Gold purity of .999 is considered pure gold and referred to as 100% gold