There are significant differences between 10K and 24K yellow gold. K, which stands for "karat," is an indicator of purity: 24K gold is virtually pure, while 10K gold is actually less than half gold.
Twenty-four-karat gold is at least 99.9 percent pure, with only trace amounts of other metals. Ten-karat gold is 41.7 percent gold and is usually combined with silver or copper.
Twenty-four-karat gold does not exist in nature. It must be purified in a difficult process involving cyanide gas. Ten-karat gold, on the other hand, is an easily made alloy.
Twenty-four-karat gold is extremely soft. A thin layer of it can be bent with your hands. Since 10K gold is alloyed with harder metals, it is more rigid.
There are few practical uses for 24K gold. It is usually made for collectors who like the idea of owning "pure" gold. Most gold bullion is made of 22K gold. Ten-karat gold is used for lower-end gold items like inexpensive jewelry and flatware.
Twenty-four-karat gold is very expensive, not only because it contains the most gold of any alloy, but also because of the costly process needed to purify it. Ten-karat gold is relatively inexpensive and is one of the most commonly used types of gold.