What is a Ruby?

And everything else you need to know so you can get the best ruby (that your wallet allows) for yourself or your loved ones...

Cartier Ruby Ring

“A gem of barbaric splendor”, as some of the world’s most beautiful rubies have been described on occasion. 

What is it about this powerful red stone that has so many of us hooked to its fiery red color?

Perhaps its utmost rarity? Or the stone's famed red glow which, when set in a woman's pair of earrings, can be recognized from across a distance at your summer garden party? (Not kidding, the best rubies have literal fluoresce under UV-light, so also under sun rays).

Whatever the reason, rubies can command the highest per carat price of any stone. This makes them one of the most important gemstones in the market. 

In this article, I'll show you what a ruby is, how it was designated in history and more importantly, the things to be aware of when buying a ruby yourself, such as the distinction to make between pink sapphires and (red) rubies and how to color grade a ruby like an expert. So you can get the best one, for yourself, and the next generations to come. (If you can find one, that is... and if your wallet allows 💰).  

Let's dive in!


What is a ruby?

Ruby is the red gem variety of corundum. So corundum is the species (or gem family) to which ruby belongs. 

Interesting side note: also sapphire belongs to that same family. 

Whenever corundum is red, we call it a ruby. When it’s any other color, we call it a sapphire and add the color prefix to it, so a blue sapphire, pink sapphire, yellow, orange, green, white, you name it. 

But a red sapphire?

Nope, doesn’t exist. 

We call that a ruby.

The chemical components of ruby are aluminum oxide with the trace element of chromium. It is that trace element chromium which gives ruby its fiery red color.

Louis Vuitton high jewelry ring featuring a centrally set African ruby, flanked by diamonds - thejewelleryeditor.com

Origin of the word ruby

Ruby comes from the Latin word “ruber” meaning red. So the stone was simply named after its color.

That’s important to know as it wasn’t until approx. 1800 that rubies were designated as belonging to the species corundum!

Before that time, all things red were considered a “ruby”. So, a red garnet and red spinel were called “ruby” too…

But more on those historical misnomers in a later blog.

How to distinguish pink sapphires from (red) rubies?

Now there’s something else interesting regarding ruby and pink sapphire that you’re probably not aware of:

As ruby and sapphire belong to the same gem family, there’s a lot of confusion or unclarity as to where to draw the line between a (red) ruby and a pink sapphire.   

In other words, how red should a ruby be in order for it to be called a ruby?

Should it be 100% red or may it have some pink or orange tints in the red?... This is an eternal discussion among experts and gem dealers as well.

Often gem dealers use this unclarity to their advantage, saying that 'color is subjective' at the end of the day. (Thereby then trying to sell the stone they have in their stock which happens to be 'beautiful'😉

Color is subjective, yes. This is one of the reasons why grading colored gemstones is far more complicated than grading diamonds.

However, there are several guidelines that can definitely help you determine what is considered a 'better stone' in the market. (Read on for those 3 elements that gemologists look at when color grading a colored gemstone).

But also, where there is unclarity, there is room to negotiate. So let's look on the bright side.

ruby rings

Left: Cartier Ruby and Diamond Ring, jewellerydoctor.wordpress.com; Right: A Ruby and Diamond Ring, Cartier Paris - phillips.com

This matters because it has a big impact on the price in the market.

Pink sapphire has a price close to that of blue sapphire. 

Ruby brings a substantially higher price that escalates into the stratosphere as it goes over 2 carat already (provided it’s a good quality stone).

You may be able to find an 8 or 10 carat blue sapphire (although also incredibly rare if the stone is of good blue, natural and without treatment)...

But to find a ruby that size (of good red, natural and without treatment) is practically impossible!

They are beyond rare.

And far more rare than colorless - white - diamonds of that size!

For example, let me show you the most expensive ruby ever auctioned to date:

sunrise ruby cartier ring

It concerns the Sunrise Ruby, a 25.59 carat Burmese ruby set in a ring by Cartier, which sold in 2015 at Sotheby’s in Geneva for $30.4 million USD and ended up netting $1.19 million USD per carat.

No colorless diamond of similar quality has ever reached that price.

Let me repeat that: no colorless or white diamond has ever reached that price at auction!

Rubies of that quality come into the realm of prices associated with colored diamonds and jadeite jade which makes all three of them belong to the world’s most expensive gemstones - at least when we look at auction results.

Are pink and red really so different?...

Besides a big price difference between the red and pink variety of corundum that you should be aware of, there’s another fun fact that has to do with color theory which gemologists try to follow when assessing a gemstone’s color.

And that is that pink and red are actually the same color!

Pink is red going towards blue. See the color wheel below, on the right.

pink sapphire to royal red ruby lotus gemology

A great color stone scale (by the gem lab Lotus Gemology, based in Bangkok) showing how close pink sapphires are to rubies, and the color wheel.

Pink is red except with a paler saturation and a lower tone.

The right gemological term for pink actually is: purplish red.

So, how should you 'color grade' a ruby?

This brings me to the final point of this first part of the Gem Tales: color grading.

And to what I said before: 

  • How red should or can a ruby be in order for it to be called a ruby?
  • Are some secondary colors, like pink or orange, even allowed?
  • If so, how much can they be present?
  • What does the market love and what is considered “top” color in case you'd like to buy your own ruby?...

Of course, we want a ruby to be red. 

But pure hues rarely exist in nature.

So, gemologists look at 3 things when assessing a colored gemstone’s color:

  • The hue, i.e. color. We try to determine the stone's primary and secondary color.
  • The saturation, i.e. the intensity of the hue.
  • The tone, i.e. the presence or absence of blackness / darkness in a stone.

When it comes to the hue, the primary color of a ruby should be red (of course). Ideally around 85%.

The secondary color in a ruby’s red, can be orange, pink, violet or purple for about 10-15%.

Burmese ruby tends to have a hint of pink added to the red mix which is one of the reasons why they’re so desirable. (There's also another reason why they're so coveted which I'll share with you in the upcoming Gem Tales...).

When the secondary color, however, is present for more than 20% in the red, the stone’s value comes down into the commercial price range. 

Continuing with the saturation, what we’re looking for is basically a bright, vivid color.

The brighter, the better. 

The redder the red of a ruby, the more valuable the stone will be and the more expensive it will be as well.


Because that pure red hue is so incredibly rare to find in nature. And colored gemstones are valued on the basis of their color. It's their main asset.

(Unlike diamonds which tend to be colorless/white and which are mainly judged on cut).

We don’t want any grey or brown hints in the color. Ideally. Because that's very hard to find.

ruby ring on hand

For example, if a Burma-type ruby appears dull, it’s because of a grey secondary mask.

And Thai rubies tend to have a brown tint to them, which most of us don’t like that much…

Now what makes Burmese ruby so special and coveted, is not only that the red has a hint of pink in it (in fact, it’s a hint of blue but when that mixes in with the red, it creates a pinkish hue) but it has Ruby and diamond ring.

this secret super power in the form of UV fluorescence which super charges the saturation of that special type of ruby.

But more on that in one of my next, upcoming Ruby Gem Tales!

Finally, the tone

Ideally, we want a medium to dark tone for ruby of about 75-80%. Then ruby reaches its ‘optimum saturation’. 

When the tone is less than 50% it will probably be a pink sapphire (remember that red and pink are basically the same color except that pink is red with a lighter color saturation and lower tone).

In the red zone

Those percentages above are not set in stone btw! And it’s not as if gem dealers or gemologists measure the color of a colored gemstones so mathematically all the time, if ever…

Color remains subjective, yes, and it’s very hard for a group of people (also experts!) to agree on what exactly the color is in a color stone, let alone use the same language around the world when describing a stone's color. 

However, it goes without saying that experts and gem dealers who deal with colored gemstones day-in, day-out have trained their eye muscle much more than the regular consumer and so they can help you along the way (but like caveat emptor, you should also do some preparatory work as a buyer, esp. when you like to invest in a higher priced piece).

It’s of course also a matter of what you consider beautiful and whether you’re prepared to pay that price for the stone lying in front of you.

However, those above percentages - which I got myself from the great book "Secrets of the Gem Trade" by Richard W. Wise - are a good indication for consumers and hopefully helpful in guiding you along in case you’d like to invest in a colored gemstone piece.

To make matters even more, uh, challenging:

Experts disagree on which is the best secondary color in their eyes. 

Many prefer a ruby to be red-red of course.

However, some say they like a bit of orange as secondary color as it pumps up the saturation of the red and creates the best ruby. To them.

Others may prefer a slightly pinkish hue. As said, that color is usually considered the most beautiful in the market as it comes close to the coveted Burmese ruby. 


I hope the above helps you on your gemstone piece journey and if you need any help in creating your own bespoke gemstone piece, feel free to contact me here or at info@evagemsandjewels.com

You can also follow me on Instagram (@evagemsandjewels), where you can catch my Gem Tales via Instagram Live or IGTV and follow the journeys of these exquisite stones. 

Now a small Quiz for those who’d love to test their knowledge and thereby enter the Insider Gemstone Club 😉 Shoot your answers over to me via Instagram personal message and I'll go through the answers!

1. What chemical elements does ruby consist of?

2. Does a red sapphire exist?

3. Are pink and red 2 different colors?

4. When were rubies designated as belonging to the correct species of corundum?



  • Secrets of the Gem Trade by Richard W. Wise
  • Gemstones by Vladyslav Y. Yavorskyy
  • My own lecture notes of my gemology education at AIGS (the Asian Institute of Gemological Sciences in Bangkok ;))
  • The inspiring webinars by famed gemologist Rui Galopim de Carvalho (follow him @portugalgemas)

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