The word carat or karat comes from the carob tree, which regularly produces a seed of 0.20 g that is used as a landmark since ancient times. It is used for weighing precious stones or for calculating the mass of gold or silver included in the metal.
In the 1920s, the metric carat was adopted for calculating the weight of gems. To differentiate them, we write the Karat Gold with a K (or Kt), and the Metric Carat is written Ct.
Carob tree
Carob tree seed
Perfectly pure gold in jewelry is rarely used in the Western world, because the metal is soft and may warp.
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24 Kt : Composé d’or à 99 %
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22 Kt : Composé d’or à 91%
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18 kt : Composé d’or à 75%
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14 kt : Composé d’or à 58%
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10 kt : Composé d’or à 41 %
The rest of the components increase the strength of the metal and influence the color, here are some assemblages:
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Yellow Gold: Half silver and copper
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Rose Gold: More Copper and Less Money
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Red Gold: Copper only
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White Gold: Silver or palladium or nickel
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Green Gold: Silver and Cadmium
Pure gold crystal