Ruby (from Latin: ruber "red") is the pink to red-blood variety of the mineral corundum.
Prices of rubies are primarily determined by colour. The brightest and most valuable red called "pigeon blood" commands a large premium over those of a similar quality. The red hue comes from traces of the mineral chromium. Myanmar (Burma) is famous for producing the greatest amount of top quality ruby with fine, clear, deep-red colouring. The majority of these are found in the Mogok Valley. All Burmese rubies were born from a metamorphic process whereby they are usually poor in iron which results in a strong show of red fluorescence, making them different from their cousins from basaltic deposits in Thailand or Africa. All rubies have natural imperfections in them such as need-like rutile inclusions known as "silk". A stone without such inclusions may indicate that the stone has been treated.
Because of the ruby's brilliant red hues, they are often related to themes concerning the essence and vibrancy of life. If there is one gemstone that represents the passion of love, it's the ruby. However there used to be a time when rubies where looked upon as a gem that could transform the women wearing it into a mesmerizing beauty.
Corundum can exhibit a star-like phenomenon known as asterism. When viewed with a single overhead light source shined directly into the stone, a six-ray pattern across a cabochon-cut stone's curved surface is displayed, in the shape of a star.
A phenomenon known as chatoyance or cat's eye effect (from French: œil-de-chat) can be exhibited on a corundum ruby when cabochon-cut. The effect can be likened to the sheen off a spool of silk: the luminous streak of reflected light is always perpendicular to the direction of the fibres, when the fibres are parallel to the base of the finished stone to the surface of the cabochon-cut.
The Smithsonian's National Museum of Natural History has received one of the world's largest and finest ruby gemstones. The spectacular Carmen Lúcia Ruby, 23.1-carat Burmese ruby, set in a platinum ring with diamonds, was donated by businessman and philanthropist Peter Buck in memory of his wife Carmen Lúcia. While sapphire, emerald and diamond gems weighing hundreds of carats exist, high quality Burmese rubies larger than 20 carats are exceedingly rare. Which is probably something the Burmese King would like to know more about, as just like King Louis IX of France who ruled that no commoner can own a diamond, the King (known as the "Lord of Rubies"") ruled that all rubies that are over 6 carats will belong to him