More importantly - what does this mean for you & your jewelry?
Karat is how we measure the purity of gold, with 24K being 99.9% gold. Another way of looking at it is 24 out of 24 possible parts are gold -- beautiful, pure, straight-out-of-the-ground gold!
So when we say 18K, what we really mean is 18 parts gold to 6 parts other alloyed metals. For all you math whizzes out there: 24 parts pure gold divided by 18 gives you 75%. 18K gold consists of 75% pure gold and 25% other metals.
Why not use 24K for everything?
Pure gold is extremely malleable and not particularly durable, especially for jewelry you wear everyday. A 24K ring scratches, dents and bends easily, requiring constant attention and repair.
Alloying with other metals increases durability by making the gold harder and less malleable. That way an engagement ring or wedding band can be worn everyday for decades.
Alloying also changes the color of gold.
Yellow gold is often alloyed with silver, copper & zinc which help maintain its buttery color.
White gold needs some assistance from alloys like platinum, palladium, nickel & silver to appear silvery in color.
Rose gold uses copper as an alloy to achieve its pinky hue.
What is the best karat gold?
The truth is, there is no such thing as the BEST karat gold when it comes to jewelry. It depends on the type of jewelry, how often you will be wearing it and your lifestyle.
If your considering what karat to choose for a wedding ring that you will be wearing every single day - 14K may be a good choice as it has 41.7% alloyed metals making it durable enough to handle daily wear and tear. Some people prefer 18K for it's vibrant yellow color. However, it is softer and will need a little more TLC over many years of wear.
Say you're choosing a necklace or earrings for special occasions, you could go for a higher karat gold because these types of jewelry don't see the same heavy wear and tear that a ring would.