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Sapphires and Rubies: Chemically Identical

Aug. 18 2014
Ruby and sapphire engagement rings are chemically very similar and yet their price varies greatly. So, what are the differences between rubies and sapphires?

We have chatted a lot about sapphire engagement rings lately but while out on my morning walk with Lemon Tree the other day, I was listening to an interesting programme about the chemical composition of sapphires and how, from a chemical point of view, they are almost identical to rubies.

I had never considered this before but the more I thought about it, the more I realised that there is a huge range of colour variations of sapphires and yet rubies are always red. Did this mean then that rubies were red sapphires?

What Are The Differences Between Rubies and Sapphires?

Both gemstones are a form of corundum mineral and have indistinguishable properties; they both rate at a 9.0 on the Mohs hardness scale and both boast a refractive index of 1.757-1.779. They even have the same specific gravity of 3.99-4.0.

So, scientifically speaking they are the same and yet we consider them to be different. Why?

Their colours, availability and price distinguish these two beautiful stones, which are both often used as the centre stones for ruby or sapphire engagement rings. I had always known that rubies were red and thought that sapphires were blue, but what I did not know was that sapphires constitute all other corundum colour varieties including pink, orange, yellow and green. Rubies can only be red.

18ct yellow gold and Ruby by beth Gilmour

18ct yellow gold and Ruby by beth Gilmour

What Makes a Ruby Red?

This fascinating programme went on to explain that the ruby red colour is caused by the chromium and that the colours in sapphires are the result of iron, titanium and other chromium impurities. When I got home I was telling L about my discovery and she asked me where you drew the line between pink sapphires and light red rubies.

She was right to ask this question, as apparently there are no rules on what shade of red equates to a ruby and what shade of pink equates to a sapphire.

When I checked on the net there was lots of advice for escaping rogue jewellery sellers trying to sell pink sapphire engagement rings as the more valuable light ruby alternative.

What about the Price of Sapphires and Rubies?

Real rubies are quite rare and the darker ones with the blood red colour are the most desirable. Sapphires are more common and often found in larger carat sizes than rubies, making them more versatile.

Pink Sapphire Beaten Ring by Alexis Dove

Pink Sapphire Beaten Ring by Alexis Dove

This availability issue is reflected in the large price difference, with rubies being much more of an investment.

The Meaning of the Ruby and the Sapphire

Ruby or sapphire engagement rings, for me, have to have real significance and I was interested in whether rubies and sapphires have similar meanings and associations, but apparently not. Rubies denote passion, good luck and personal inspiration, as well as protection, while sapphires are linked to sincerity, faithfulness and divine knowledge.

Fascinating to see how two stones so chemically identical can actually be so different in value and meaning, but the more I research gemstones, the more I appreciate how intriguing this world is. I am addicted!


Stepan TerteryanLondon
Daniel GallieLondon
Jon DibbenSurrey
Deborah CadbyLondon
Mirri DamerCornwall