Ruby

The Sanskrit word for ruby, ratnaraj, is loosely translated as lord, king, or leader of precious gems, and for more than a millennium, ruby has been the king of colored stones. Ruby’s value accounts for its exalted status. The price per carat of top-quality large rubies easily surpasses that of any other colored gem, except colored diamonds. Its deep-red, saturated hue is the standard against which every highly prized red object is measured, whether it’s ruby red Texas grapefruit or ruby red lipstick. Magical powers have long been associated with the gem—ancient ruby amulets warded off bad luck and evil spirits, and, more recently, ruby slippers helped send Dorothy (and Toto, too) back home to Kansas.

The name ruby originates from the Latin ruber, meaning red. Gemologically, ruby is one of a dozen or so varieties of the species corundum, which includes sapphire in all its forms and colors. But to gem enthusiasts, ruby is the most important corundum and the most coveted available red gem of all.

History and romance. Rubies were sought for their incredible color. Almost any red gem was compared with ruby, named after ruby, or misidentified as ruby. Probably the most historically significant, the 170-ct. Black Prince’s Ruby, is not a ruby at all, but a spinel. The stone is mounted in its original natural rough state as the centerpiece of the Imperial State Crown of England.

Color variations. Plainly stated, ruby is red. Secondary nuances of orange, pink, and purple are common, but if any of those colors predominate, the gem is classified as sapphire.

Qualities. Rubies from Burma (Myanmar) are considered the finest. They’re typically endowed with an intense, saturated red color and a strong red fluorescent glow. Many show a pinkish or orangy secondary color, which many gem enthusiasts find appealing.

The “classic” Burma ruby has been found in the Mogok district, 400 miles north of the capital, Rangoon, for more than 800 years. Like mining areas everywhere, the region produces all qualities of ruby.

Recently, the Mong Hsu mining district, southeast of Mogok, has released thousands of carats of poor-quality gems—also known among dealers as “fish tank gravel.” When heated, however, Mong Hsu “gravel” transforms into attractive gemstones that display “Burma” color but cost a fraction of what Mogok ruby costs.

Until recently, Thailand was an important source of ruby. Its mines, in an area called Chantaburi, near the Cambodian border, were famous. Lately, rubies have been discovered in Afghanistan, Pakistan, East Africa (Kenya, Tanzania, and Madagascar), Thailand, Cambodia, and Vietnam. Small pockets of gem-quality ruby have been located elsewhere around the globe, but they don’t hold sufficient quantities to become major sources.

Value. Ruby follows the same rule as most other colored gems: The more saturated the color, the more highly prized the stone. Subtleties in color can affect value dramatically. Secondary colors of purple and orange, typical of Thai and African stones, don’t add value and, in a fine-quality ruby, may even detract from it. Pinkish overtones that are not overpowering—a quality typical of Burmese stones—can catapult a ruby’s value.

Size matters when it comes to fine-quality ruby. Burmese gems over 5 cts. are extremely rare, but they do turn up. Burma Mogok rubies as large as 20, 30, and 40 cts. have been reported.

Some of the ruby from India and Africa occurs in opaque, non-gem qualities. It’s not uncommon to see such material in 5- to 10-lb. boulders or carvings, often mixed with green zoisite. Because of their size, some large opaque rubies have been appraised—improperly—at millions of dollars. Five dollars per pound is a more likely estimate of value for material fit for paperweights and doorstops. Carvings are priced according to artistry.

The latest prices. Burmese ruby weighing 1 ct. in extra-fine quality can range from $2,800-$4,500 per carat to $4,500-$8,000 per carat. Burmese rubies weighing 5 cts. of the same quality can go for as high as $20,000-$30,000 per carat or more, if they come with certificates and can be proved to be Burmese with no enhancements. More affordable fine-quality 1-ct. ruby from other localities (assumed heat treated) range in price from $1,500-$2,000 per carat and $2,000-$2,600 per carat, according to The Guide.

Enhancements. Nearly all ruby—by some estimates, 99.99%—is heat-treated to improve color. Heat increases the red or removes a common sapphire-blue component. It also reduces the visibility of inclusions, by dissolving them or by healing fissures. Thai, Sri Lankan, and Mong Hsu Burma stones are almost always heat-treated, and even some Mogok rubies have been treated (which may surprise purists). Mong Hsu rubies often have numerous cracks and are heated at very high temperatures to repair them; other fractures and cavities are filled with glass. Color enhancement is permanent. Because there’s a dramatic price difference between untreated and treated ruby, enhancements should be disclosed to your clients.

Care and cleaning. Like all corundum, which ranks 9 on the Mohs scale, ruby is difficult to scratch. It can tolerate moderate heat and ultrasound, but its value dictates caution in the cleaning or repair of ruby-set jewelry.

Bench settings & precautions. Gem ruby’s growth process creates a strong aluminum-oxygen bond, which is difficult to break. As a result, ruby can stand up to most bench activities, but modest precautions are appropriate.

Proper identification is important. Some heat-treated rubies are actually diffusion-treated colorless sapphire. Such gems are as durable as any ruby or sapphire, but the red color resides only in the top surface. If a stone is chipped or repolished, the color layer could be affected.

Recommended reading. For more information, see the following:

  • Ruby & Sapphire, by Richard W. Hughes (RWH Publishing, 1997).

  • Gem and Crystal Treasures, by Peter Bancroft (Western Enterprises, 1984).