Gemmologist’s Corner – Sapphire and Ruby

Gemmologist’s Corner – Sapphire and Ruby

15 July

Did you know that Ruby and Sapphire are made from the same material – the mineral Corundum?

If pure, Corundum is colourless, the red or blue (or other shades of sapphire) are a result of metallic ‘impurities’ in the crystal pocket deep within the earth where the gems form. Chromium gives Corundum it’s red colour – Ruby – and the amount present determines the depth of colour, sapphire gets its blue tone from Iron and Titanium. Other solid ‘impurities’ found in these stones are called ‘inclusions’ and help gemmologist identify stones and can help identify the origin. For example dissolved needle crystals give ruby and sapphire it’s characteristic growth lines which identify the stones as being natural immediately. Perhaps the most sought after sapphires come from Kashmir in India and are known for their magnificent ‘cornflower blue’ colour, they are no longer mined here and therefore command exceptionally high prices at auction when they come up, the most distinctive inclusion is a small black crystal. More commonly occurring sapphires are ‘Ceylon’ or Sri Lankan, they can be identified by zircon crystals with a stress crack around them called a ‘Zircon Halo’. ‘Star’ sapphires display a six rayed star effect or ‘asterism’ when cut ‘en cabachon’ this effect is caused by long needle crystals lying in three dimensional planes. Impurities in gemstones can very useful in identifying the stone, giving it a particular colour or intensity of colour and also an array of beautiful optical effects when viewed in light and certainly make them unique, interesting and beautiful!

My favourite examples in this sale are

Lot 62 – A pair of purple sapphire cufflinks, relatively inexpensive compared to their blue counterparts the stones in these cufflinks will be an interesting addition to any Gentleman’s attire €300 – 400

Lot 62

Lot 35 – A suite of eternity rings, each set with ruby, blue sapphire or pink sapphire – the most popular corundum colours displayed here in the ever popular ‘stackable’ suite €1800 – 2500

Lot 35

Lot 199 – Madagascar Sapphire and diamond cluster ring, if you can’t afford a Kashmir sapphire, this blue will rival the cornflower blue of the elusive Kashmiri sapphires for a fraction of the price €2500 – 3500

Lot 199

Lot 283 – An Art Deco synthetic sapphire ring, synthetic sapphires became popular in the early 20th century with the development of new technology, this is a 9.00 ct fine example and will only set you back €4000 – 6000

Lot 283

Lot 311 – A yellow sapphire and diamond ring – sapphires come in a rainbow of colours and this is a pretty example of a yellow sapphire that will brighten up anyone’s day €600 – 800

Lot 311