„We hear about historical, large diamonds, but large rubies of perfect colour and great purity are mythological.”“
-Robert Gordon, British Ambassador, 1888
Ruby has always been prized for its deep red colour. This ranges from rich purple to a deep blood red. The small inclusions, often referred to as “silk”, belong to its well-known and beloved characteristics.
The ruby is known as one of the most famous gemstones. And almost everyone immediately has the image of a blood-red piece of jewelry in their mind at the mention of the name. But do you know the ruby’s closest relative? No? You will be surprised, it is certainly known to you, even though the two do not really look alike. Because the stone is mostly deep blue, more precisely it’s the sapphire.
But how can it be that two gemstones with completely contrasting shades go through an almost identical process of formation? The answer is provided by his chemical approach.
From a purely chemical point of view, both ruby and sapphire are corundum, a relatively common mineral. Ruby is not a mineral in its own right, but a red variety of corundum, whereby the colour spectrum can vary between pale red and dark red. The mineral corundum itself is almost colourless and also occurs as “common corundum”, without gemstone quality.