You may remember from one of our previous blog posts that the weights of diamonds and other gemstones are measured in carats. Well, confusingly, the word “karat” is also applied to gold, but in that case, it’s a measure of purity rather than weight. (Sometimes the word is spelled with a C when applied to gold, but using the K makes it at least slightly easier to denote units of weight vs. units of purity.) Is your head spinning yet? Never fear, your expert Austin jewelers at Copeland Jewelers are here to explain!
Gold is a very soft metal, which means that pure gold can be problematic when it comes to making jewelry (or any other item that will be used a lot in different environments). Pure gold is easy to bend or scratch (remember the stereotypical image of the pirate biting into a gold coin to see how soft it is?), which means that if your jewelry is made from pure gold, you’re likely to end up with pitted pendants, folded rings, and marked-up bracelets – and heaven forbid you accidentally drop an earring back and then step on it!
To combat this issue, most gold jewelry and coins are made from alloys, or mixtures of different metals, today. Commonly, gold is alloyed with copper and/or silver, which are, of course, still high-quality materials. One karat is equal to 1/24 pure gold, so if something is made of 10-karat gold, it’s 41.7% pure gold, and the other 58.3% is made of other metals. 18-karat gold is 75% pure and 25% other metals. Gold that is 100% pure is referred to as 24-karat. The most common karatages for fine jewelry are 10-karat, 14-karat, and 18-karat. Sometimes jewelry is, in fact, made from 24-karat gold, but it should only be worn on rare occasions and must be cared for extremely carefully to avoid damage.
Sometimes the non-gold metals that make up a gold alloy are specifically formulated to change the color of the finished product. For example, pink or rose gold is achieved with higher concentrations of copper; white gold is made with nickel; and green gold comes from silver and zinc combined with pure gold.
The word “karat” comes from the same source as the word “carat” that denotes the weight of gems: the carob seeds that were used in ancient times to measure weight. Around a thousand years ago one German mark coin weight 24 carats and was made of pure gold. As it became easier and more popular to combine gold with other metals, people became concerned with measuring gold’s purity and co-opted the word “carat,” eventually changing the first letter for clarity’s sake. In the United States, the Federal Trade Commission (FTC) regulates karat value and the purity of jewelry. The FTC requires that all jewelry with a karatage of ten or high be stamped with either “K,” “Kt,” or a number denoting its percentage of pure gold.