Ruby The red variety of Corundum, the mineral group that contains Ruby, Sapphire, and Emery.

History

Classification and Grading

Characteristics of Ruby

Evaluation

Treatments and Enhancements

Buying a Ruby, Things to Consider

Bibliography

History

Rubies have been highly prized and valued as a gemstone since early times. In ancient India, the Sanskrit language has a number of names for this noble gemstone. Ratnaraj - the king of precious stones, Ratnanayaka - leader of precious stones, and Padmaraga - red as the lotus, show that this stone was held in high esteem by the ancient Hindus.

From the mineral family Corundum, whose name can be traced through the Latin, ruber,  to the Sanskrit word kuruvinda and the Tamil word, kurundam, all of which can be defined as ruby. Ruby is the red variety. All other colors of the Corundum gemstone family are considered to be Sapphire. Thus all Rubies are Sapphires but only red Sapphires are Rubies. This distinction between Ruby and Sapphire did not become known until 1800 before which most red stones, i.e., Garnet and Spinel, were considered to be Rubies.

In ancient times, Ruby was considered to have magical properties that would be bestowed on the wearer. These included wisdom, wealth and romance as well as peace and invulnerability. In Roman times they were considered with other red stones as carbunculus.

Over the centuries Ruby was considered to also have medicinal and curative powers and many references to ruby elixirs can be found in apothecary and early medical texts.

Large gem quality rubies have always been a rare commodity. Some of the more famous Rubies include the 137 carat Rosser Reeves Star Ruby, which is on display at the Smithsonian Institute, the 100 carat Edith Haggin de Long Star Ruby, exhibited at the American Museum of Natural History, and the 167 carat Edward Ruby, on display at the British Museum of Natural History and the 43 carat Peace Ruby named for its discovery in 1919, the end of the First World War.

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Classification and Grading

Ruby can be defined as opaque, translucent or transparent Corundum with medium to dark tones of red to purple-red in color. Corundum that is light or very light in tone are more properly called pink Sapphire.

Over the years a number of terms and classification nomenclature has been used to describe gem grade Ruby. These include:

• Burmese, Burma or Oriental Ruby - The finest qualities have traditionally been called Burmese. These fine grades are characterized by the deep, intense pure red color with a hint of blue, often described as "Pigeon's Blood" and usually have no undesirable under or over tones of color.
• Thai Ruby - Stones mined in the region formerly known as Siam are characterized by dark red tones with brownish overtones sometimes resembling garnet in color.
• Ceylon Ruby - Stones mined on the island of Sri Lanka, formerly Ceylon are characterized by a bright, lighter shade of red with strong brilliance and purity of color.
• African Ruby - Usually found in small sizes, these stones are characterized by a purplish red color.

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Characteristics of Ruby

• Chemical Composition - Aluminum Oxide (Al₂O₃) with Chromium Oxide causing the red color associated with Ruby.
• Crystallography - Hexagonal System characterized by six sided prisms terminated by flat faces.
• Hardness - 9 on the Moh's Hardness Table
• Cleavage - None
• Fracture - Conchoidal, splinter, brittle
• Characteristic inclusions - Ruby often contains Rutile or negative crystals, called "Silk." These are often found arranged in three sets of intersecting lines that are instrumental in stones that display asterism. Other commonly found mineral inclusions are Zircon, Mica, and Spinel.
• Fluorescence - Strong red

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Evaluation

Only a very small percentage of mined material can be called high quality since the vast majority of stones, once cut, display inclusions, silk, clouds or uneven color distribution. Rubies that are flawless under 10X are extremely rare and most stones show some level of imperfection.

It should be understood that the most important element of value in Ruby is the intensity and purity of color with red or slightly purplish red being the most highly valued. Stones with a brownish cast or those exhibiting orange overtones are less desirable.

Cutting style and quality have significant bearing on value as the depth of stone contributes greatly to the overall appearance of a stone's color saturation. In addition the orientation to the original crystal structure has dramatic effect on the resulting color display.

Evenness of color, lack of surface imperfections, quality of final polish and symmetry are important in the overall evaluation of fine Rubies as well and are important to the final evaluation of any stone.

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Treatments and Enhancements

The most common treatments and enhancements of Ruby are:

• Heat Treatment - rough stone is heated to very high temperatures resulting in usually permanent enhancement of color.
• Dyes, laminates and impregnated waxes are sometimes seen but are not permanent and should be avoided.

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Buying a Ruby, Things to Consider
 

There are three elements that should be considered when buying a Ruby.

Color - Look for intense pure red color with little or no undertones of brown. Striping and uneven coloration is common in lower quality stones and should be avoided.

Clarity - Inclusions are very common and their size and location should be carefully considered. Rutile crystal inclusions are referred to as Silk and when evenly distributed can produce a sheen in transparent Rubies and the asterism seen in Star Rubies.

Cut - Rubies are often cut in their countries of origin. Many of these stones were cut with emphasis on creating the heaviest stone from the rough crystal instead of cutting for the beauty achieved with proper proportion and orientation. Although Ruby is the next hardest stone to Diamond, surface imperfections such as pitting and striation should be at a minimum. Finally an even finish polish and quality of facet placement and symmetry should be considered.

Ruby prices have increased dramatically over the last few years with many older sources being depleted and with nationalization of some mines restricting export and trade. Fine stones today can command per carat prices that are comparable to Diamond prices.

Because of its hardness, Ruby can be safely used in all types of jewelry including rings and bracelets and unlike more brittle stones, such as Emerald, can be safely bezel set.

Bibliography

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