Why Are Gems and Gold Measured by Carats and Karats?

The words carat and karat are similar-sounding words, but they refer to two entirely different things. The carat is the standard unit of measurement for the weight of gemstones, while a karat is used to indicate the proportion of gold in an alloy.

The weight of a carat is 200 milligrams or 0.2 grams, and its weight was standardized at an international conference in 1907. But why is it called a carat?

Hundreds of years ago, people had no standard for the weight of gems, so they used the carob seed of the carob tree as a base unit of weight. One seed was designated as weighing one carat. The weight of the gem could then be determined by the number of carob seeds it equaled in weight since, at the time, it was believed that carob seeds had a uniform weight.

But there was a problem with this system of measures based on the carob seed. There are variations in the weight of each seed from a single pod of the carob tree. So how did it become such a relied upon method?

A study in 2006 from the Royal Society: Biology Letters looked at the problem. They discovered that human selection of uniform seeds might have played more of a role in using the seeds as a measure than the supposed uniform weight of the seeds themselves. They found that people could differentiate the differences in the…