All about Ruby

One of the four "precious" stones, the ruby has been valued and imitated down the ages. The great value of rubies is mentioned in the bible, and they have been mined for at least 2,500 years in Sri Lanka and Burma. As well as being prized as jewels, rubies are also used in the electronics industry to produce red lasers and in some recording equipment.

What is ruby?Back to top

Ruby is the red form of corundum, an aluminium oxide and one of the hardest substances known to man. The rich red colours come from the addition of small amounts of chromium within the crystals. The name comes from the Latin word for red, rubeus. Frequently faked and imitated, true rubies are one of the most valuable and prized gemstones.

What makes a good ruby?Back to top

Large, high quality rubies are more valuable gram for gram than even diamonds, they are so rare. Anything over 2 carats in size will either be very, very expensive or a fake. The most prized rubies are those with a perfect red colour, without a trace of blue or brown (so-called pidgeon's blood rubies). Some rubies contain small, needle like inclusions called "silk", which, if skillfully incoporated into the cut, can resemble a six pointed star and add greatly to the stone's value. If you are buying gem-grade rubies, they should be examined closely for symmetry and under a variety of lighting conditions.

Ruby is often heat treated to improve the colour and remove blue/purple tinges. Other common treatments to ruby are to use glass or borax to fill in small fissures in the surface and improve the appearance, ideally this should be avoided as the filler can fall out or break over time. Synthetic rubies are made from powdered Aluminium oxide and a colouring agent, which are fused together under intense heat. Without expert knowledge, these can be very difficult to tell apart from natural stones, but are obviously of far lower value and quality. The presence of "silk" can be one clue that this is a true ruby.

Other red gems that are often passed off as rubies include garnet, purple sapphires and red spinel. Rubies are generally harder than the other gemstones and the red colour richer and deeper rather than sparkling and clear.

How to care for rubiesBack to top

Rubies are incredibly hard wearing and difficult to break. Second only to diamond in their hardness, they do not share diamond's vulnerability to sharp blows are there is no easy cleavage plane. They can be cleaned by most methods of jewellery care and the most realistic worry is probably going to be the setting.

Famous rubiesBack to top

A lot of famous rubies, such as the Black Prince's ruby, are actually red spinels, perhaps illustrating how difficult it can be to tell the two apart (or possibly illustrating the gullibility of famous men). Some famous true rubies that are also on display include the 167 carat Edwards ruby in the British Natural History Museum in London, and the uncut 196.1 carat Hixon ruby at the Los Angeles Museum of Natural History.

Myths and legendsBack to top

Many, many magical and mystical properties have been ascribed to rubies. The Burmese thought they were the blood of Mother Earth and in Hindu mythology it is referred to as the "king of precious stones". Rubies are said to bring the wearer romance, courage and peace

Place of originBack to top

The best-quality rubies are still produced in Burma, but Thailand and Cambodia are also major sources. Bangkok is the most important trading centre for rubies and is where most of the cutting and polishing techniques were developed. Kenya and Tanzania also produce rubies, but rarely of gemstone quality.

Technical informationBack to top