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The Gemstone Ruby

Ruby is distinguished for its bright red color, being the most famed and fabled red gemstone. Beside for its bright color, it is a most desirable gem due to its hardness, durability, luster, and rarity. Transparent rubies of large sizes are even rarer than Diamonds. Ruby is the red variety of the mineral Corundum. Sapphire, the other gem variety of Corundum, encompasses all colors of Corundum aside from red. In essence, Ruby is a red Sapphire, since Ruby and Sapphire are identical in all properties except for color. However, because of the special allure and historical significance, Ruby has always been classified as an individual gemstone, and is never identified as a form of Sapphire (though some purplish-red colors may straddle the line of being classified as either Ruby or Sapphire).
Chemical Formula Al2O3
Color Red
Hardness 9
Crystal System Hexagonal
Refractive Index 1.76 - 1.77
SG 3.9 - 4.1
Transparency Transparent to opaque
Double Refraction .0008
Luster Vitreous to adamantine
Cleavage None, but may exhibit parting
Mineral Class Corundum


The color of Ruby ranges from bright red to dark reddish-brown. The most preferred color is a deep blood red with a slightly bluish hue. Such Ruby is known as "Burmese Ruby" or "Pigeon's Blood Ruby". Ruby from Burma is famous for its exceptional coloring, and has traditionally produced the finest Rubies. However, Burmese Ruby rarely exceeds several carats; large flawless Burmese Rubies can be worth millions of dollars. Many Rubies on the market are from Thailand, and these Rubies have a less-desirable brownish hue, though they often can be heat treated  to improve color. Heat-treating a Ruby can also increase its transparency by removing tiny internal flaws.

Inclusions of tiny, slender, parallel Rutile needles in Ruby cause a polished gem to exhibit asterism. A Ruby displaying asterism is known as a "Star Ruby", and if transparent can be very highly prized. Star Rubies exists in six ray stars, though twelve ray stars are also known. Rubies must be have good transparency to possess gem value. Opaque or semi-opaque Rubies have relatively little value, even if they display asterism.

The same Rutile inclusions that are responsible for asterism in certain Rubies can also decrease transparency and cause a hazy effect known as silk. Though Ruby can be one the most expensive gemstones, it also comes in more dull opaque forms that are fairly inexpensive, and are often polished into cabochons. A unique gemstone form composed of opaque red Ruby in contrasting green Zoisite is well known from Tanzania, and is used as a minor gemstone and can be carved into ornaments.

The color of Ruby is usually caused by minute inclusions of the metal chromium. These impurities are often responsible for causing a Ruby to fluorescent, which can be helpful in its identification. Ruby is also pleochroic, and will sometimes display a lighter and more intense color when viewed at different angles.

Ruby is a tough and durable gem, and the only natural gemstone harder than Ruby is Diamond. Despite this, Ruby is still subject to chipping and fracture if handled roughly, and care should be taken to ensure it is properly handled.

Ruby was first synthesized in 1902. The process of creating synthetic Ruby is known as the Verneuil process. Only experts can distinguish between natural and synthetic, lab-created Ruby.

Ruby is one of the most popular gemstones, and is used extensively in Jewelry. Ruby is used in all forms of jewelry, including bracelets, necklaces, rings, and earrings. It is used both as centerpiece gemstone in pendants and rings, as well as a secondary stone to complement other gemstones such as Diamonds. Star Ruby is polished as cabochons, and, if clear, can be extremely valuable.

Large Ruby gems are extremely rare and valuable. Fine colored Ruby with a deep red color and excellent transparency can reach several thousand dollars a carat. Synthetic Rubies are inexpensive and often used as a cheap substitute for natural rubies.

Ruby is the birthstone for July.


Many deceitful names are given to less valuable red gems in connotation with Ruby. Many of these names are used by unscrupulous dealers to confuse inexperienced buyers. Generally speaking, any time the word Ruby is used with a prefix (except for those outlined above), it is a fake or a less valuable red gemstone. The red Garnet gemstone Pyrope is particularly vulnerable to be called Ruby with a tacky prefix. The list below describes false names for Ruby that are in fact Pyrope:
Adelaide Ruby
American Ruby
Arizona Ruby
Australian Ruby
Bohemian Ruby
California Ruby
Cape Ruby
Colorado Ruby
Elie Ruby
Montana Ruby
Rocky Mountain Ruby

Beside for Pyrope Garnet, other red gemstones have also been assigned false names in connotation with ruby. These include:
Alabandine Ruby - Almandine Garnet
Ancona Ruby - Rose Quartz
Balas Ruby - Pink to pale red Spinel
Brazilian Ruby - Pink Topaz
Copper Ruby - Cuprite
Garnet Ruby - Red Garnet
Geneva Ruby - Synthetic Ruby
Ruby Copper - Cuprite
Ruby Jack - Red Sphalerite
Ruby Garnet - Red Garnet
Ruby Spinel - Red Spinel
Siberian Ruby - Red Tourmaline
Spinel Ruby - Red Spinel
Verneul Ruby - Synthetic Ruby

Rubies are often heat treated to improve color as well as burn out certain inclusions. It is common industry practice to heat treat Rubies, and untreated Rubies with excellent natural can be exceptionally valuable.

A recent practice in the gemstone industry is to fracture-fill Rubies to conceal flaws. This is done by heating them in molten lead glass which has a very similar refractive index to Ruby gemstones. Fracture-filled Rubies are significantly cheaper than their more authentic counterparts, and because of this one should always buy Ruby from a reputable dealer.

The center of Ruby gemstone trade is in Bangkok, Thailand. The Chantaburi Province in Thailand has always been an important source of Rubies, producing gems with excellent clarity but with less desirable browner tones. However, the color of Thai Rubies are able to be improved by heat treatment. The Thai Ruby deposits were exhausted in the 1980's.

The most valuable Rubies with the finest natural color come from Mogok, Burma (Myanmar). There are strict trade embargoes and restrictions again Burma for its human rights violations, and several countries, especially the United States, ban any exports from this county. The Ruby mines of Mogok have been under the tight control of the Junta government; however, a new very significant Ruby source was discovered in Burma in 1992 in Mong Hsu. The color of these Rubies aren't as good as Mogok, but they too can be improved through heat treatment.

In 2000, new Ruby sources were discovered in Madagascar (in Vatomandry and Andilamena). These deposits turned out to be very extensive and productive, and Madagascar is now one of the leaders in Ruby output. Other important Ruby sources include Sri Lanka, India, Cambodia, Vietnam, Tanzania, and Mozambique. Other sources of Ruby include Afghanistan, Pakistan, Tajikstan, Australia, and the U.S. (North Carolina).

Ruby is identical in appearance to Ruby Spinel. In fact, many old famous red gemstones thought to be Rubies were determined to actually be Spinel. Ruby and Spinel often occur together in the same mineral environment and localities. The most famous ruby, the Black Prince's Ruby, set into the royal crown of England, was once thought to be the largest cut Ruby, until scientific analysis determined it to be in fact Spinel. Garnet (particularly Pyrope) and red Tourmaline (Rubellite) may also resemble Ruby, though Ruby is significantly harder.

Ruby PHOTOS [Click photos for more details]

Ruby IN THE ROUGH PHOTOS [Click photos for more details]

Ruby JEWELRY PHOTOS [Click photos for more details]
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