Rubies get their distinctive colour from the levels of chromium and iron in their makeup which can manifest as a range of red hues, from pink or purplish to orange or brown.

Gem-quality red corundum are all rubies, and any other gem-quality colour variations are sapphires, which we traditionally associate with a deep blue colour, though they do come in greens, pinks, yellows, and more. What gives these gems their distinctive colour? In the case of Kashmir sapphires, fine silk inclusions scatter light and give the gem a soft appearance. Emeralds, for example, often feature long hollow tubes as part of their structure and may not devalue the gem. Whilst high clarity is often a priority for many, inclusions (especially in emeralds and sapphires) can be part of their charm. The clarity of gemstones is determined by qualities such as transparency, blemishes, and inclusions. Beryl is formed from beryllium aluminium cyclosilicate with traces of chromium and vanadium. All three stones have a hexagonal crystal structure.Ĭorundum is formed of aluminium oxide, with traces of chromium and iron in rubies, and traces of iron, titanium, chromium, and other elements present in sapphires.

They also both have no gemstone cleavage, which means they lack planes in the crystalline structure with weak atomic bonds, making them hard to split.Įmeralds are a variety of the beryl family of gemstones and are not quite as hard as rubies or sapphires, but they are still very solid and have an indistinct gemstone cleavage. Physical and chemical propertiesīoth rubies and sapphires are varieties of the corundum family of gemstones, meaning they are dense and compact, and are the second hardest natural mineral, with diamonds being the hardest. Most people are familiar with diamonds, but how well do you know the other three gems? Here, I have put together some information on the technical aspects of rubies, sapphires and emeralds. There are only four precious stones – diamond, ruby, sapphire and emerald – and all other gemstones are known as semi-precious. When we talk about gemstones, you may be familiar with the terms precious and semi-precious stones.

Corundum ruby sapphire