The rarest form of the mineral Corundum, rubies are renowned for their redness in colour. Oval and cushion cut are popular shapes for ruby stones but their hardness means they are suitable for faceting in any cut.
Rubies were first mined in Asia and were used as decoration on armour. It was believed that rubies brought good fortune so they would be laid beneath the foundations of buildings to secure a strong long lasting structure.
The intense dark red that the ruby is famed for comes from an element known as chromium. Chromium comes from the Greek word 'chroma' meaning colour.
The colours of rubies are valued by three components, hue, saturation and tone. Hue is the colour, saturation is the brightness and tone is the shade or depth of colour. Like sapphire, rubies have primary and secondary hues. In rubies the primary hue is red with secondary hues of pinks, oranges and purples. As with other colored gemstones, it is not uncommon for rubies to be treated with heat to enhance the colour intensity. Colours vary from pale red to pigeon's blood red, the most desirable colour of all for ruby which is a very dark red with a hint of blue.
The clarity of a ruby is measured similar to a diamond, a clear stone without imperfections will be classed as a premium ruby gemstone.
If you own ruby jewellery, remember it's a gemstone known for its hardness, store separately in order to prevent it scratching other pieces of jewellery or metals. To wash your ruby jewellery, use warm soapy water and avoid harsh chemicals as this can damage the intense colour.
In the past rubies have been discovered in Thailand, India and Africa. However more recently, large deposits of rubies have been discovered under the receding ice shelf of Greenland.
Traditionally, Burmese rubies were considered the best, but for political reasons they're not currently available. Most now originate from Sri Lanka and Thailand.