Why Are Rubies Red ? The Fascinating Reason Behind Their Color

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Rubies are notoriously beautiful red stones that capture the hearts of many. While not as often talked about as sapphires, rubies are just as precious and beautiful as their blue siblings. In fact, they’re one and the same thing, a form of corundum. The difference is that rubies have a distinct chemical makeup that gives them a red color, and sapphires have a different chemical makeup that gives them that cornflower blue color.

But why are rubies red ? Is the red always a striking deep crimson or do they come in different shades ? And what’s this about rubies in watches, where are they in a watch ? Let’s find out !

ruby red

Why are rubies red ?

Rubies owe their red color to trace amounts of chromium. Rubies are a form of crystalline aluminum (otherwise known as corundum) and the chromium replaces some of the aluminum, resulting in a reddish color. The red in rubies can be faint or very saturated, and depending on where and how the impurities are dispersed throughout the crystal the clarity may also be affected.

Like sapphires, rubies can be heat-treated to impro their color, remove impurities, or even improve asterism (a star-like optical effect).

All rubies are red, or at least a shade within the red family. Along with diamonds, emeralds, amethysts and sapphires, rubies were one of the old cardinal gemstones. They’re also one of the toughest gemstones, so any jewelry made with rubies is bound to last.

Rubies also come in pink, purple, and orange

Rubies may also be found in reddish pink, pink, orange, deep red, nearly brown, a purply red, and it all depends on the amount of chromium present in the ruby and how it’s dispersed.

Some rubies are faint and cloudy, some are brilliant and have a very good color. The rubies we are most accustomed to are the deep red rubies, and they may form this way or may be treated to become this way.

The shade of red and how clear the ruby is can be enhanced, usually by baking the gemstone at 1400 C for 20-30 minutes. Of course the process is more complex than this, since various pastes and powders may be added to the ruby to enhance clarity, fill gaps or cracks.

Some rubies have a sort of impurity present, called silk. This silk catches the light and disperses it within the gem, leading to a very beautiful stone. But if the ruby is heat-treated, the silk dissolves, leading to higher clarity and a deeper, better color. It’s a bit of a trade-off, depending on what you like more.

Read also: Jewelry And Skin Tone

Why are rubies used in watches ?

Rubies are used in watches because they are a type of corundum, which is a very tough precious stone, almost completely scratch-resistant. Because of this, rubies have a very stable structure once cut, and they can take a lot of heat.

As the various moving parts within a watch do their job, the whir and tick and click and spin, generating friction and thus heat. Metal elements in key points would get stuck after a while, they would meld together, or they would corrode.

Ruby, being so tough and durable, is a perfect option for long-lasting and accurate watches. Accuracy means the different elements never stop working, making sure your watch never goes too fast or too slow.

The most likely place you’ll see the rubies is the watch movement, which may show on the front in some watches. Those are small red circles made of (usually synthetic) rubies.

Are other jewels used in watches ?

You may also find sapphire cases on watches, and in some watches it’s just the front glass. Most jewels that are also durable are pretty expensive, so they’re not often used in watches (aside from rubies).

However you may fine watches adorned with various jewels. For example the Piccadilly Royal Princess watch is made entirely out of emeralds, including the face of the watch. It’s later been made of other jewels, but the original is emerald.

Does the number of jewels in a watch matter ?

In the end the number of jewels in a watch has become irrelevant. There was a time, when watches first started using rubies (jewels) to improve accuracy, that the number of jewels did matter. The number of moving parts that were made of actual ruby mattered, because it meant the watch would last a very long time and be accurate.

However not all watch parts need to be made of jewels. Watch buyers paid attention to how many jewels were in the watch – back then a marker of quality – but soon companies started adding jewels in places where the watch did not need them. The result was an overabundance of jeweled watches, with no real use.

So buyers stopped caring about the jewels in a watch and this is rarely mentioned nowadays. The law now states that the number of jewels on the watch must reflect the number of actual, useful jewels in the watch.

Read also: Ruby Engagement Ring Meaning 

What other gemstones are like rubies ?

Rubies are great for a pop of red color, but they’re not the only ones you can get if red is what you’re after. They are indeed the toughest possible red stone, except for a lab-grown red diamond.

But there are plenty of other options to choose from if you’re looking for a red hue in your stone, and you’d like to try something else. Here’s a list of the most common and beautiful red gemstones that are not rubies.


Garnets are commonly found in reddish hues, ranging from a warm yellow to orange to red, and all the way to a deep, warm brown. Because of this you’re likely to find a shade of garnet that suits your preferences quite easily.

These are not the toughest of stones, ranging from 6.5 to 7.5 on the Mohs hardness scale. But they will still shine brightly for you and with a proper, protective setting like a halo or bezel they will survive just fine.

Red zirconia

Red zirconia is another common red stone, and it’s very affordable. Cubic zirconia is a form of lab-grown diamond alternative, and it can be easily cut and shaped into whatever you like. It can be made into different colors as well, all you have to do is ask for a red one and your jeweler can provide it for you.

This gem is a bit tougher than garnet, but not as tough as ruby. It scores an 8-8.5 on the Mohs scale so it may not need a halo setting, but it should still be kept safe.

Red moissanite

Red moissanite is hard to come by in nature, so your best bet is to go for a synthetic one. Along with cubic zirconia, moissanite is a great alternative for diamonds and it does come in any color you want. Meaning you can easily get your in a beautiful shade of red if you ask your jeweler to provide it for you.

Moissanite is significantly tougher, scoring a 9.25 on the Mohs hardness scale. For comparison, rubies score a 9 while diamonds score a perfect 10. This means you can set your moissanite any way you like, it doesn’t need the extra protection. However if your favorite jewelry design features a protective setting for the gemstone then go right ahead.

Red beryl

Red beryl is a pretty rare stone, but you can find it if you look hard enough. It usually comes in cool shades like blue and green, but you may get lucky and get a red one. This stone ranges between 7.5 and 8 on the Mohs scale, so it may need some protection.

Red topaz

Topaz is a little easier to find in a reddish hue than beryl, but finding it in pure red may be difficult. You can find it in warm colors ranging form yellow to brown, and then in various tones of pink and wine. If you’re not very picky about the shade of red then topaz can be a good match for you.

This stone scores an 8 on the Mohs scale, so it may need a slightly protective setting.

Red spinel

Red spinels are not very well known, but they can be found by your jeweler. They come in different shades and colors, and red is a fairly common one. This stone is 7.5-8 on the Mohs scale, so it may need a small amount of protection.

Red tourmaline

Tourmaline is actually a very beautiful stone, and it’s famous for it’s two-toned colors. You can get tourmaline in many colors, including red, and if you’re looking for something extra eye-catching you can go for the ‘watermelon one’ which ranges from a deep pink to a light green.

On the Mohs scale this stone is a 7-7.5 so it will definitely need protection as it can be pretty brittle.

Fire opal

We’ve reserved fire opal for last, because it’s both stunning and very different from ruby. Opals, as you know, come in different color and they have something like iridescent effects all throughout the stone. Most opals are a milky white with greenish hues. However you can also find orange-red opals with gold iridescent effects.

Those are commonly called fire opals, and they’re always cut in a round, polished shape. It’s a 5.5-6 on the Mohs scale so a chunky, polished appearance is the safest way to cut this stone. Always use a protective setting for this one, it may crack.

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