A member of the corundum family, ruby is the red version of sapphire. This gemstone has a hardness of 9 and a refractive index of 1.6, making it as precious as diamond. Depending on the deposit, certain ruby varieties are more sought-after than others due to their formation. How is a ruby formed? What are the main deposits? Planetys gives you the answers.
How is a ruby formed?
Like sapphires, rubies are created by the combination of very specific minerals to produce corundum, of which ruby is the red variety. This formation takes place between 25 and 50 km underground. As in Australia, these depths are characterized by very high temperatures, and the pressure exerted on the rocks allows new crystals to form. This is how all rubies are formed, with the exception of Cambodian and Thai rubies. Rubies from these two countries come from alluvial deposits that are very rich in basalt (at depths of 2 and 5 m).
For metamorphism to take place, the parent rock must contain aluminum and silicon of the composition Al2SiO5. To give rubies their intense red color, certain aluminum ions in the parent rock are replaced by chromium. The largest rubies are formed when the mixture takes a long time to cool. If, on the other hand, it cools very quickly, this can prevent or limit the formation of this gem.
Ruby deposits around the world
The main ruby deposits
Ruby is mined mainly in Asia, in Myanmar, Thailand, Sri Lanka and Vietnam. But also in Madagascar, Mozambique, Tanzania, Kenya, Afghanistan, Tajikistan and Pakistan.
Myanmar deposits
Myanmar is the world’s leading ruby producer. These deposits, located in the Mogok region, produce some of the rarest and most beautiful rubies on the planet, with few inclusions. The intense red color (with a pink tinge) of these gems extracted from Burmese deposits makes the country’s rubies the most coveted in the world. The famous “Pigeon’s Blood” ruby is found in these deposits.
Deposits in Thailand, Cambodia, Sri Lanka and Vietnam
Rubies from Thailand or Siam are currently very present on the gemstone market. These deposits are located in the country’s border region with Cambodia. Rubies from these countries share the same geological origin. They are easier to mine than rubies from other countries, but of inferior quality.
Sri Lankan deposits produce beautiful rubies that are slightly lighter than Burmese rubies. Their colors range from raspberry red to light red. Gems extracted from Vietnamese deposits are virtually identical in quality to Burmese rubies, but with better purity.
Deposits in Madagascar, Mozambique, Tanzania and Kenya
Already the world’s second-largest sapphire producer, Madagascar also produces rubies, whose best and most resplendent specimens are sought after the world over. Most of the gems extracted from this country’s deposits are reddish-brown to purplish. In just a few years, Mozambique has become a ruby-producing giant. Gradually, its stones are replacing those of the former Burma, whose production is steadily declining.
Tanzania is the country with the oldest ruby deposits in Africa. These gems are sumptuous and of excellent quality. Kenya’s deposits also produce rubies of a quality comparable to those of Mozambique. Some specimens can reach 20 carats, making them unique.
Deposits in Afghanistan, Tajikistan and Pakistan
Rubies produced in Afghan deposits are extremely beautiful and very rare, as are those from Tajikistan and Pakistan. The stones from these three border countries have the same origins. The finest rubies from these deposits have nothing to envy of Burmese specimens.
