Karat
The karat is 1/24 (or 4.1667 percent) of the whole amount of metal, making 24 karat gold pure gold. 14 karat gold is gold comprised of a ratio of 10 parts alloy to 14 parts gold, or an alloy of gold containing 41.7 alloying metal and 58.3 percent gold.
Rose Gold Alloy Metal
The alloy used to make rose gold is commonly either copper or a combination of 90 percent copper and 10 percent silver.
History
The usage of the karat for measuring gold quantity comes from the medieval coin known as the mark, which weighed 24 carats.
Considerations
Pink gold may define a rose gold with more silver in its alloy, and red gold may be used to refer to gold with more copper or only copper in its alloy.
Features
On the Moh's scale of hardess (a relative hardness scale ranging from one to 10, 10 being the hardest) rose gold rates 2.5 and melts at 240 degrees Celsius.