Why Are Rubies Red? What Gives Them Their Unique Hue?

why are rubies red

Like many jewels, rubies are loved for their entrancing appearance. Rubies are the most vibrant shade of natural red in existence. Even when viewed under bright lights, rubies maintain an exquisite deep red color. But how is this possible when most gemstones are translucent under a microscopic lens and flashlight? 

Well, rubies are not just any other gemstone, and contrary to the popular saying that beauty is in the eye of the beholder, rubies are arguably one of the prettiest gems around. There’s something about the captivating color of rubies that makes them undeniably gorgeous. 

There’s a reason why rubies are coined “The King Of The Gems.”

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It’s official, rubies are a gorgeous gemstone. But the question remains: why are rubies red? Let’s find out! 

Where Are Rubies From?

To answer why rubies are red, we must look at the origin of rubies. Rubies were first discovered in the Mogok Valley of Upper Myanmar, formerly Burma. 

Even though rubies were first discovered in Myanmar, they also come from many other countries around the world.. Additionally, Mogok Valley rubies are not necessarily the most exquisite and enchanting rubies either. 

In fact, in 1992 a discovery was made in the city of Mong Hsu. Also located in Myanmar, Mong Hsu appears to have triumphed over the Mogok Valley in terms of providing a greater supply of rubies.  

Following these discoveries in Myanmar, rubies were discovered in many other countries around the world. Rubies are so highly valued that some places are exclusively devoted to mining rubies, including: 

  • Afghanistan 
  • Cambodia 
  • India 
  • Madagascar 
  • Nepal 
  • Pakistan 
  • Tanzania 
  • Thailand 
  • The United States of America 
  • Vietnam 

In the U.S., only a handful of states source rubies, including Montana, North Carolina, South Carolina and Wyoming. As you can see, rubies come from all over the world. So let’s get straight to the burning question in your mind: why are rubies red?

why are rubies red

What Causes Rubies to be Red? 

As part of the trigonal crystal system, a classification system by which crystals are categorized, rubies fall into the oxide mineral variety. When gemstones are colorful their appearance is often attributed to an element or compound within the gems. This is the case for rubies, which get their signature red color from chromium, an element naturally found in the world around us. 

Though it’s simple to say that chromium accounts for the redness of rubies, the circumstances that create this redness are more complex. Let’s briefly backtrack for a moment. We subtly mentioned that rubies are gemstones of the oxide mineral family. 

As such, rubies are gemstones comprised of corundum, a mineral composition containing a combination of oxygen and aluminum. Naturally, it’s easy to assume that these two elements come together to create corundum. But corundum alone is not enough to generate such a striking red color. In fact, on its own rubies would be translucent and clear like diamonds, because corundum is a colorless mineral. 

That’s where chromium comes into the picture. 

Chromium exists in the periodic table under atomic number 24. As a transition metal, chromium is commonly used in stainless steel and has the ability to reflect about 70% of all visible colors. 

Is that why rubies are red? We’re getting closer.

What Chromium Does to Rubies

Rubies form when about 1% of chromium is substituted for aluminum. What does this mean? Even though oxygen and aluminum are present in rubies, they are not responsible for the redness. Are you still with us? Great! We have an answer for you: Rubies are red due to the trace amount of chromium within the gemstone. 

The most fascinating detail about rubies is that the intense redness is completely natural. The perfect redness that rubies exude might trick you into thinking they are artificial or manmade. If there’s anything we’ve learned from examining gemstones, it’s that Mother Nature weaves a beautiful paintbrush throughout our world, and a prime example is the redness of a ruby. 

Let’s dive deeper. 

why are rubies red

How Does Chromium Turn Rubies Red?

Now that we know what makes rubies red, let’s reveal how chromium transforms a colorless compound into something as radiant and red as rubies! As we mentioned, a trace amount of the aluminum found in corundum is replaced by chromium. 

Since there is an even number of electrons in the purest form of corundum, it does not absorb any light. What happens when no light is absorbed? If you guessed that light is reflected, you are correct! 

But rubies are not solely made from pure corundum. They contain chromium, which does not have an even number of electrons. 

This enables chromium ions to absorb most wavelengths of color. The result is a radiant reflection of red. And just like that, rubies appear red solely because of the presence of chromium atoms. 

While this process might seem a tad complex, it really boils down to one fundamental: 

The way an object’s atoms are arranged directly correlates to the colors that we see. In the case of rubies, chromium atoms absorb light in a way that reflects the color red. 

How Rubies Compare to Other Gemstones

Why do we see rubies as red and not their sister gemstone, blue sapphires? 

Since the color red is reflected by chromium atoms, we see rubies as being red. Similarly, when blue is reflected by chromium atoms, we see blue. Rubies are often compared to sapphires because at their core, rubies are essentially identical to sapphires, with the red color being the sole difference.

Did you know that rubies are actually far rarer to find than diamonds? A common misconception is that diamonds are the leading gemstone in terms of quality and admiration, but the truth is that rubies hold much more value than diamonds.

While a diamond is the only gem that is stronger and more durable, rubies are simply more novel thanks to their deeply saturated red tone. And as you can imagine: the redder a ruby, the higher its value. 

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