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Rubies are mined in Africa, Asia, Australia, and Greenland. They are most often
found in Myanmar, Sri Lanka, Kenya, Madagascar and Thailand, though they have
also been found in the U.S. states of Montana, North Carolina and South Carolina.
The Mogok Valley in Myanmar has produced some of the finest rubies. However in
recent years very few good rubies have been found there. In central Myanmar the
area of Mong Hsu also produces rubies. In 2002 rubies were found in the Waseges
River area of Kenya. Rubies are being mined at Audilamena in northeastern
Madagascar. Sometimes spinels are found along with rubies in the same geological
formations and are mistaken for the more valuable gem. However, fine red spinels
may approach the average ruby in value. Rubies have a hardness of 9.0 on the
Mohs scale of mineral hardness, and among the natural gems are only surpassed by
diamonds in hardness.
Ruby gemstones are valued according to several characteristics including size, color,
clarity and cut. All natural rubies have imperfections in them, including color
impurities and inclusions of rutile needles known as silk. If the silk inside of the stone
is absent, then one could assume that the stone was heated at a temperature of 3000
degrees, which is done to give the ruby a better color of red. Usually the rough stone
is heated before cutting. On the other hand, artificial rubies may have no
imperfections. The fewer the number and the less obvious the imperfections, the
more valuable the ruby is; unless there are no imperfections (i.e., a "perfect" ruby),
in which case it is suspected of being artificially made and its status as a priceless
gem is therefore not completely assured. Some manufactured rubies have dopants
added to them so that they can be identified as artificial, but most require
gemological testing to determine their origin.
Rubies come in various shades of red, red purple and red orange. A medium toned
red or red with slight blue is most desired. Clarity of the stone and inclusions are also
taken into account to determined the stones value. Once the stones looks more
toward the color purple or orange then it is called a fancy sapphire. Rubies
occasionally show asterism when cut into a cabochon. When they show this, they are
referred to as "star rubies." They can sometimes be more valuable than normal
rubies because asterism is rare.
The world's biggest ruby is the Rajaratna Ruby, which weighs 2,475 carats (495 g).
Because the Rajaranta shows asterism, it is also the largest star ruby. The world's
biggest double-star ruby (with a 12-pointed star) is the Neelanjali Ruby, weighing
1,370 carats (274 g). Both rubies currently belong to G. Vidyaraj from Bangalore,
India. A 8.62 ct. Burmese ruby sold for $ 425,000 per carat (2,125,000 $/g) or $
3,800,000 on Feb. 15, 2006 at Christie's in Switzerland.
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