It is also an extremely rare gemstone, especially in finer grades. Next to diamond, ruby is the most expensive stone in the world in sizes over three carats.
The finest-quality rubies are still believed to be those from the Mogok region in Myanmar (Burma), but these days, new sources of supply in India, Africa, Vietnam and Thailand have made lovely rubies in all sizes and colours more readily available.
Ruby is a member of the corundum family and has the chemical composition of crystallised aluminium oxide.
This group, consisting also of sapphires, is the hardest of all known coloured stones outside of diamonds, and while it presents itself in various shades, only the red colour is classified as ruby.
Indeed, it is to its colour that the gem owes its name, derived from the Latin word ruber, meaning red.
While pure corundum is colourless, ruby owes its blushing hue to the presence of chromic oxide, which also causes ruby to glow with fluorescence under ultraviolet light.
Sometimes, minute traces of iron are present in the ruby's crystal lattice, imparting a brownish tint. Other inclusions are fine lines of rutile, zircon crystals, liquid-filled cavities and so forth.
These inclusions differentiate natural rubies from synthetics; however, a ruby's transparency is of secondary importance as inclusions do not impair the gem's quality unless they decrease the transparency of the stone or are located right in the centre of its table.
Ultimately, it is ruby's colour that is its most-defining characteristic and it has long been associated with the elements fire and blood, implying warmth and life for mankind. Indeed, legend has it that Epiphanius, the bishop of Seville who wrote many influential medical science texts, believed strongly in ruby's fire.
Epiphanius wrote liberally of the gem's profound ability to generate heat – so much so that when placed in water ruby would reportedly cause the liquid to boil. "The inextinguishable fire that glowed within the ruby could not be hidden; it would shine through any cloth or material that was wrapped around it," he wrote.
Like no other gemstone, ruby is the perfect symbol for invoking powerful feelings. A ring set with a precious ruby does not symbolise a calm and moderate sympathy, but a passionate and unbridled love that two people might for each other.
Just as diamonds are the gems of romance, ruby is the gem of passion, housing the profound power of the heart's desire in its very core.
It is believed to banish sadness, protect its wearer from ill fortune, assure tranquillity and peace, and rid one's mind of nightmares.
From the 1300s-1600s, ruby was believed to preserve bodily and mental health. In line with this, Middle-Eastern physicians were known to prescribe a concoction of finely-ground ruby in fruit juice, used to rid one of fear and promote joy.
Other uses were an aid for eye ailments and diseased livers. In modern times, ruby is the July birthstone and 15th and 14th anniversary stone.
Being so hard, ruby does not scratch easily and can be cleaned in an ultrasonic cleaner.
Variety of: Corundum
Found: Thailand, Myanmar (Burma), Australia, India, Sri Lanka, Brazil, Vietnam and Africa.
Modern birthstone: Ruby
Traditional birthstone: Ruby
Mystical birthstone: Ruby
Ayurvedic birthstone: Ruby
Cancer (June 21 – July 22) Emerald, Moonstone, Pearl, Ruby
Leo (July 23 – August 22) Tourmaline, Onyx, Sardonyx