1854, variant spelling variant of carat (q.v.). In U.S., karat is used for "proportion of fine gold in an alloy" and carat for "weight of a precious stone."

Unit of measurement describing the content of gold in a jewelry item or ornament. Pure gold is extremely flexible and bends easily, and is thus alloyed with more durable metals when used in jewelry to [..]

An American spelling of carat.

A measure of the purity of gold. Pure gold is 24-karat.

The Karat, like all jewelry, is an indication showing the purity of metal, such as gold, representing the purity.  In gold, 24k is pure, while 18k is 18 parts pure and 6 parts other metal.

The unit of measure for the fineness of gold. Fine gold is 24 karat (Kt). Other common standards are 18Kt (750 fineness), 14Kt (583 fineness), and 10Kt gold (417 fineness)

A unit of gold fineness (and gemstone weight). 24K is pure gold, whereas 18K gold is 75% pure.

the proportion of pure gold in an alloy. Pure gold is 24 karat, with lesser quantities of gold represented by a fraction. For example, 18 karat gold is 18/24 or 75% gold, 25% non–gold alloying metal. [..]

A measure of the amount of pure gold in a metal. One karat is 1/24th of the total weight of the object. 100 percent pure gold is 24 karats.lusterThe manner in which a mineral reflects light.

Unit of measurement describing the content of gold in an ornament. The karat unit measures the percentage of gold in metallic objects made of gold (mainly jewelry). Since pure gold bends too easily, i [..]

Karats are a unit of measure indicating the fineness of gold. Gold in its purest state is referred to as 24-karat gold. Most gold jewelry is actually made from a gold alloy containing gold and another metal or metals. Pure 24k gold is normally too soft for use in jewelry, so jewelers mix gold with another metal like nickel or silver to harden it, c [..]

carat, karat