Ruby is a red color variety of corundum mineral, it Is «brother» of sapphires in chemical composition and structure. The best untreated samples can compete in price with very expensive colored diamonds. Ruby is considered the most valued gemstone. On auctions the best samples cost over 1 million USD per carat. Ruby is a corundum mineral colored with chrome and possess red color with pink, orange and violet shades. Pure spectral red color without additional shade is the most valued. In commerce the expression «Pigeon Blood» can be used for description the best bright red color. This color can also be specified in a certificate.
Physical properties of ruby let apply this mineral as perfect jewelry material. Red corundum has a hardness of 9 in Mohs scale, it is a very durable mineral and is not prone to scratching a surface of facets. Opaque rubies are cut in cabochon shape. If a corundum sample contains inclusions of oriented rutile needles, then such stones may show the effect of asterism. They are usually translucent or opaque. If you shine a flashlight on a cabochon, then a bright 6-ray star will appear on a surface of a cabochon. Combination of rarity and high characteristics of red corundum is typical to Burmese deposits. Today, untreated Burmese rubies are among the most desirable gems in the world. These are investment level precious stones; over the past 10 years, their price has soared more than 7 times. Today, specimens from Mozambique are widespread on the world market, mining in this source were started only a few years ago. In beauty, they can be compared with the Burmese, but their price is significantly lower. Experts note that African samples are now undervalued, and their cost will increase significantly in the near future.
In the northern Myanmar (Burma), in the Mogok valley, beautiful high quality corundum specimens are mined. Burmese ruby is a well-establish brand in the world of precious stones. Unheated «Pigeon Blood» stones from Burma are the most expansive, gem-quality rubies are very rare. Nowadays, a large market share is occupied by stones from Mozambique. They can be as attractive as the Burmese samples, but at the same time their price is much lower. Also stones come from Thailand, Madagascar, Tajikistan, Tanzania, Vietnam and other countries. The “expensive” Burmese origin must be confirmed by a certificate from a reputable gemological laboratory.
Mohs scale hardness:
4.00 g / cm3
red, orangish-red, pinkish-red
Mogok is a valley in the north of Burma, a source of the best and the most expansive rubies in the world.
There is no consensus among gemologists where there is a clear boundary in color between pinkish-red rubies and fancy pink sapphires.
The name «ruby» from ancient Sanskrit means “ratnaraj”, which is translated as «king of precious stones». Bright red color is associated with the strongest human emotions: love, passion, anger. Rubies are mentioned in the Bible. Physical properties of this stone were described by roman scientist Pliny the Elder in the Ist century AD. Ruby was very popular among European royal families and the upper-class. Many medieval europeans wore jewelry with rubies to guarantee health, wealth, wisdom and success in love. As symbol of passion it became an ideal romantic gift. That is why today engagement rings with rubies tend to rise in popularity. Nowadays red corundum shows the fastest increase in comparison with other stones.
Optical and quality properties of corundum are often improved by enhancement. The most common method of enhancement is heat treatment. It is applied to more than 90% of all mined rubies. As a result of heating, the visible characteristics can be improved. The color may become more saturated, it is also possible to remove unwanted shades (such as purple), that reduce the cost of a sample. During heating some typical inclusions also melt, as a result clarity of a stone improves. The cost of uheated samples is about 2-3 times higher than heated samples with the same quality. The cheapest treated rubies are filled with lead glass. Glass filling is a method that applied for improving transparency of low quality stones, usual African. After enhancement opaque rubies can become transparent, but they cost just 1-20 US dollars per carat.
The photo of faceted sample from Myanmar (Burma), natural (untreated). Weight is 2.56 ct
In the photo: untreated tajik rough piece
In the photo: the ruby «Pigeon blood» in heart-shape, 5.07 ct, Mozambique. Without heat treatment.
The photo of natural pinkish-red ruby, Mozambique.
The photo of cabochon with asterism phenomena weighted 27.69 ct, Vietnam.