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This precious gemstone originates from the ruber rubrum, which is Latin for red. They have a hardness of 9, and are one below diamonds making them a perfect stone to be used in a piece of jewellery that will be worn every day, such as an engagement ring.

Ruby is the name given to the red corundum and is found in any shade of red ranging from red, pinkish, purplish, or brownish red. The colouration in this stone is dependant on the amount of chromium and iron content within the stone.

The overall colour can often, but not always give a clue to a stone’s geographical origin; Burmese stones tend to be purple to reddish colours, and Thai stones appear more brownish red.

Most authorities expect a medium to dark tone, naming stones lighter than this as a pink sapphire.

All of the corundum family have a long history of heat treated enhancement to the stones, this is usually done under a very high temperature and controlled cooling, this is often done to clarify the stone to improve the tone and saturation of colour. This heat treatment does not decrease the value in the stone by a lot.

Natural rubies are exceptionally rare, but artificial ones can be manufactured by the verneuil process.

They are mined in Africa, Asia, Australia, and Greenland. They are most often found in Myanmar, Sri Lanka, Kenya, Madagascar, Thailand, and have also been found in the US, but the Mogok Valley has produced some of the finest rubies.

Sometimes spinels are found alongside these fine stones and the same geological formations are mistaken for the valuable rubies, however fine red spinels may approach the average ruby in value.

Value is measured by size, colour, clarity and cut and are the most valuable of the corundum family. Larger sized stones can be of more value than the comparably sized diamonds and certainly rarer.

All have some sort of imperfection to them, which include many colour impurities and inclusions of rutile needles know as silk. If there are no traces of this silk then we can presume that this particular stone has been enhanced by heat at a temperature of approximately 3000 degrees, however artificial rubies may not have any imperfections. The fewer the imperfections, the more valuable it normally is unless there are no imperfections, which is suspected to be an ‘artificial ruby’.

Rubies can occasionally show asterism when the stone is cut into cabochon; this is sometimes referred to as a star. These can sometimes be more valuable than normal due to the asterism being very rare. This is known as a star ruby.

The world’s largest example is the Rajaratna Ruby, which weighs 2,475ct (495g) because Rajaratna shows asterism; it is also the largest star ruby. The world’s biggest double-star ruby (with a 12 pointed star) is the Neelanjaliu Ruby, weighing 1,370ct (274g).

The chemical composition is aluminium oxide which is also called corundum and this is the same as sapphire. In fact rubies are really sapphires but with the presence of impurities such as chromium oxide and iron oxide giving them their colour. Varying amounts and types of impurities will cause different shades and depths of colour, ranging in colour from a deep blood red to a light pink colour.

The most celebrated source of these wonderful and dramatic gemstones is the northern, Myawmar region of Burma. However, other areas in South East Asia, Tanzania and Kenya also mine rubies. In the 19th century they were considered more valuable than diamonds though this has now changed.

This gemstone is the birthstone of July and over the years they have come to be associated with the qualities of love, enthusiasm and strength, probably because of their intense colour. It is therefore clear why they are an ever-increasing choice for engagement rings.

As rubies and sapphires are chemically the same stone, there is no distinct division between rubies and pink sapphires but historically a ruby that has a particularly pink hue is known as a pink sapphire.

This gemstone makes a wonderful and striking choice for an engagement ring.