Corundum

Le corundum is a mineral of great importance in the field of luxury jewellery, particularly for its most prized varieties, ruby and sapphire. It is a crystalline form of aluminium oxide (Al₂O₃), and its hardness ranks it just behind diamond on the Mohs scale, with a score of 9. This characteristic makes it an extremely durable and scratch-resistant stone, ideal for jewellery that needs to withstand daily wear and tear while retaining its brilliance.

Composition and properties of corundum

Le corundum is essentially composed of aluminium oxide, and may contain traces of other elements such as chromium, iron, titanium and vanadium, which influence its colours and optical properties. The most famous varieties of corundum include :

• Ruby Red corundum, coloured with traces of chromium.
• Sapphire Blue corundum, often coloured with iron and titanium. The term "sapphire" can also refer to corundum of different colours, with the exception of red.

Use of corundum in jewellery

In luxury jewellery ruby and sapphires are highly prized for their beauty and durability. Corundum's optical properties, such as brilliance and transparency, make them particularly attractive stones. What's more, their exceptional hardness ensures that they will remain intact for many years, even with daily use.

Ruby

Ruby is a form of corundum whose red colour comes from traces of chromium. It is highly prized for its vivid colour and rarity. High-quality rubies are often rarer and more expensive than diamonds of equivalent size.

Sapphire

Sapphire is another precious form of corundum, best known for its blue colour. However, sapphires can also come in a variety of other colours, including yellow, pink, green and even white. The most precious blue sapphires generally come from Sri Lanka, Burma and Madagascar.

Frequently asked questions about corundum

What is corundum?

Corundum is a crystalline mineral composed of aluminium oxide (Al₂O₃). It is best known for its precious forms, ruby (red) and sapphire (blue and other colours).

How hard is corundum?

Corundum has a hardness of 9 on the Mohs scale, making it one of the hardest minerals after diamond.

What is the difference between a ruby and a sapphire?

Rubies and sapphires are both varieties of corundum. The main difference lies in their colour: rubies are red due to the presence of chromium, while sapphires can be blue or other colours, mainly due to traces of iron and titanium.

Where can you find the best rubies and sapphires?

The most prized rubies come from Burma (Myanmar), while high-quality sapphires are often mined in Sri Lanka, Burma and Madagascar.

In conclusion, the corundum is a gemstone of choice in luxury jewellery, appreciated for its hardness, beauty and durability. Whether as a ruby or a sapphire, this gem continues to captivate jewellery lovers the world over.