When you hear the word sapphire, chances are you picture a deep, royal blue gemstone.

But sapphires have a colorful secret: they come in almost every color of the rainbow.

A Little Sapphire Science

Sapphire is a variety of the mineral corundum, made primarily of aluminum and oxygen. Pure corundum is actually colorless—the beautiful colors we see in sapphires come from tiny amounts of other elements within the crystal.

For example, iron and titanium can produce that classic sapphire blue, while chromium can create pink. Other combinations can result in yellow, green, purple, orange, teal and even sapphires that appear to change color under different lighting.

And here's a fun gemology fact: ruby is corundum, too! When corundum is red, we call it ruby. Pretty much every other color falls under the sapphire family.

Sapphire is also a very durable gemstone, rating 9 on the Mohs hardness scale, second only to diamond. That makes it a great choice for jewelry that's worn frequently.

Why Everyone Is Talking About Montana Sapphires

One variety getting lots of attention lately is the Montana sapphire.

Yes—beautiful sapphires are mined right here in the United States.

Montana sapphires are especially loved for their distinctive colors. Rather than the traditional deep royal blue, you may see soft blue, blue-green, teal, gray-blue and green. Some have a slightly moody, earthy appearance, and their color can look different as the lighting changes.

No two seem quite alike—which is a big part of their appeal.

What About a Sapphire Engagement Ring?

Diamonds may still be the traditional choice, but couples are increasingly looking for engagement rings that feel a little more personal. Colored gemstones, including sapphires, are showing up in more bridal jewelry, and it's easy to see why.

A sapphire can offer color, individuality and durability while still feeling timeless.

And you certainly aren't limited to blue. A teal Montana sapphire, soft pink sapphire or even a sunny yellow sapphire can make a beautiful and unexpected center stone.

Sapphires are a perfect reminder of one of my favorite things about gemstones: there is always more to them than what you see at first glance.

Sometimes the science behind the color makes the stone even more interesting.