What does it mean to have a ten karat gold ring or a pair of seven karat gold earrings? Why is twenty-four the maximum number of karats anyone can have?

It all has to do with alloys, a chemical blend of different elements.

Gold isn’t strong enough to function as jewelry on its own. The softness of gold plays into the old act of biting coins to see if they’d bend, as most other metals aren’t soft enough when a moderate amount of force is applied. To make up for that, most (if not all) gold jewelry is a blend of other metals – which is called an alloy.

So, what does that mean for karats? Let’s dive in.

Alloys and Their Karats

Yellow Gold

Yellow gold often has few other elements in the alloy, allowing the color from the gold to shine on its own without diluting it too much. As a result, a stronger yellow color is likely to yield a higher karat.

White Gold

White gold is an alloy mixed more often with silver, though sometimes you’ll find percentages of nickel, zinc, palladium, and/or platinum.

Rose Gold

Rose gold is commonly made using copper and other stronger metals, like silver or platinum, as copper is also a relatively soft metal.

Pure Gold

Pure gold is not an alloy, but rarely is even twenty-four karat gold “pure” on a chemical level. For those that own twenty-four karat gold jewelry, there will be minute traces of other elements that are unavoidable and extremely difficult to remove. Because they are such low percentages, often less than a percent or two, it is the purest gold that is possible.

Karats and Gold Purity

Understanding alloys provides what you need to understand karats. The purity of gold is measured on a scale up to twenty-four. This refers specifically to how many parts of the composition is gold. For instance, a twelve karat gold ring is twelve parts gold; the remaining twelve parts are a combination of silver, platinum, copper, zinc, and so on.

The Twenty-Four Karat System

But why is the method of counting karats on a scale of twenty-four instead of twenty-five (which is more easily divisible in a percentage system)?

Though the origin of the karat concept is open to historical interpretation, the use of the twenty-four system allows for naturally occurring impurities. In short, there’s more leeway, as each karat now represents slightly more than a twenty-five system would have.

Karat Engraving

Most rings will have an engraving on the inside to represent the metal’s quality. Often, you’ll find it notated with a number from one to twenty-four (though you’ll rarely see a twenty-four karat ring) and a “K” or “KT.” For example, a twelve karat ring may be marked “12K.”

However, not all jewelry will be marked. Earrings, for example, are typically smaller, so engraving the metal would either result in a too-small mark or damage to the jewelry. To understand the karat value, you’d have to seek a professional assessment.