The Corundum Family

The corundum family is made up of pure aluminium oxide which at great temperatures and pressures was caused to crystallise. It falls on the Moh scale at 9 which makes it the next hardest most durable stone after diamond. When set into jewellery corundum can suffer scratches or loose a little sharpness over time but is so tough that it is more likely the metal that will suffer first.

Corundum is naturally clear. The clear white sapphires are the purest corundum being free from any impurities which cause colouration and result in a wide spectrum of colours we find in this family.

White Sapphire Engagement Ring

Generally most corundum are sapphires unless they are a purplish red to a yellow red in which case they fall in the ruby category, the trace elements here creating the colour are chromium. In ancient Sanskrit Ruby’s name means king of precious stones. It is also said to ward off evil spirits and represents longevity and marital happiness. The colour is said to alter its hue as love wanes. Apparently according to story it is said the Catherine of Aragon’s ruby grew paler as Henry VIII transferred his affections to Anne Boleyn.

Mainly most other colours other than that of ruby are described as sapphires although there is one exception Padparadscha which is sometimes included in the sapphire grouping, it is Sinhalese for a type of lotus flower which describes the colour – a simultaneous pink and orange, these are very rare and expensive.

Sapphires – the name for which comes from the Latin ‘Sapphirus’ meaning blue, as originally it was thought that sapphires were only blue. Sapphires are more abundant than rubies and Padparadscha because their colouring agents are more abundant. Sapphires, we now know, come in many colours depending on the trace elements found. The, generally most popular, blue comes from titanium and iron. The popularity possibly to grow more due to the blue sapphire in prince William and Kate’s engagement ring. The other colours tend to be classed as fancy sapphires. Pink sapphires are becoming more popular since being more readily available as new mines were discovered in 1990. The colouring here being due to chromium. Yellow sapphires used to be known as oriental topaz before it was realised they were part of the sapphire group.. Green sapphires mostly consist of very fine bands of yellow and blue which blend when viewed with the naked eye. Green sapphires used to be called oriental topaz. Orange and lavender/violet sapphires are rare however heat treated varieties are more readily available.

Sapphires are the birthstone of September and are said to symbolise truth, serenity, harmony, peace and hope of everlasting love and apparently are also said to support mental health.

There are varieties that fall within this family that are known as phenomenon stones which incorporate colour change sapphires which change colour when viewed in different lights. When in artificial light it can be one colour or shade and another when viewed in natural light. Star sapphires and star rubies are another type of phenomenon stone. Rutile needle inclusions provide silk (silk like appearance) which when aligned at particular angles play with the light to create asterism in the shape of a star on the surface of the stone. These six pointed stars only show when the stones are cut into the cabochon shape.

Well I hope this has given you a little insight into this stunning family, I certainly know what stone I’d like in my next ring!