Colombian Emerald

A gemstone’s country of origin suggests to the jeweler/gemologist a certain quality or perceived quality. For colored gems, that generally means top color, and so it is with emeralds: More often than not, emeralds of the finest color have come from Colombia.

History. Colombian emeralds have been found in archeological digs dating back to pre-Columbian times, from the 1200s, as artifacts such as crystals set in solid gold. Tribes such as the Mayans, Aztecs, Toltecs, and Incas, as well as the lesser-known Chibcha Indians, appreciated the green gems. By the mid-1500s, when the Spanish conquistadors arrived in what is now called Colombia, emeralds had already traveled all over Central and South America.

Prior to the 16th century, Cleopatra’s Egyptian deposits were the only known source of emeralds for Europe and Asia. But after the discovery of large, clear, saturated crystals in Colombia, the Egyptian material was considered to be of only historical significance.

One of the earliest and most outstanding Colombian emerald jewels is the Spanish Inquisition Necklace, now part of the Smithsonian Gem and Mineral Hall collection. According to the Smithsonian, “The large diamonds and emeralds were probably cut in India in the 17th century, making them the earliest fashioned gems in the national gem collection. According to legend, at least a portion or variation of this necklace was once the property of Spanish royalty and later adorned ladies of the French court. Unfortunately, information concerning the details of the early history of the necklace is extremely meager. It was apparently purchased early in the 20th century by the Maharaja of Indore. In 1947, Harry Winston acquired the necklace in its present form from the Maharaja’s son. Winston sold the necklace to Mrs. Cora Hubbard Williams of Pittsburgh. The Smithsonian Institution received the Spanish Inquisition Necklace as a bequest from Mrs. Williams in 1972.”

The Smithsonian also notes that all 15 emeralds in the necklace “undoubtedly came from Colombia” (the Muzo and Chivor mines) and gives this description of the large (approximately 45 cts.), central barrel-shape emerald: “Its rich velveteen color and exceptional clarity place it among the world’s very finest quality emeralds. The shape closely approximates the form of the original elongated hexagonal crystal, suggesting that the crystal faces were simply rounded off to yield the largest possible gem.”

Katherine Hepburn wore the necklace to the Oscars in 1947, on loan from—who else?—Harry Winston.

Color. Emerald is a green beryl. In its purest form, beryl is colorless. Emerald gets its color from minute amounts of chromium and/or vanadium. The emerald variety is defined as having a medium to strong saturation of color. Therefore, light green beryls will not be classified as an emerald, but called simply green beryl.

The hue range for emerald extends from slightly yellowish-green through bluish-green. Pure green lies somewhere in the middle of this range. While many prefer a slight bluish secondary color, the majority of jewelers will opt for a more pure green hue.

Other color variations of beryl—such as red, pink, and yellow—are taking advantage of their sister’s fame and being marketed as red emerald, pink emerald, and golden emerald. (See “The Emerald Test,” p. 145.) They do have more traditional and mineralogical names (bixbite, morganite, and heliodor, respectively) but reportedly sell better under the emerald label.

Qualities. Each major Colombian emerald mine seems to produce gems with distinct qualities. For example, Chivor crystals generally have an overabundance of secondary blue hue; Cosquez stones commonly have a slight yellowish component and are smaller and more included; Muzo gems have the quintessential pure, strong, saturated dark green color. La Pita crystals are typically highly fractured, which makes them much more fragile than most.

We expect to find visible inclusions in most emeralds, and there are very few absolutely clean stones from the Colombian mines. Most jewelers and consumers know and accept this. GIA’s colored-gem grading system places emerald—along with red beryl and red tourmaline—into the Type III category, which denotes stones that are always included.

Enhancements. Colombian emeralds are usually enhanced with fillers. Cedarwood oil has been considered the filler of choice, but jewelers should understand two facts about cedarwood. First, although natural cedarwood oil exists, 90% of what’s in the market is reportedly an entirely manufactured product. And even “natural” oil must be processed for purity, which means that enhancement experts will question its natural origin. Second, like any oil, natural or synthetic, cedarwood oil eventually will leak out of the stone if not used in conjunction with a sealer.

Palma, used in the majority of Colombian stones, is also called Araldite 6010, or Epon 828 (made by Shell and Du Pont). This is a pre-polymer and lasts as long as—if not longer than—traditional oils such as cedarwood.

Permasafe is an epoxy-resin product similar to opticon, also called 224 in the trade. It’s used with a hardener, which helps prevent leaking. However, discoloration in the form of a milky appearance is likely over time. Unlike opticon, this material is much more difficult to remove, especially from stones of La Pita origin.

Processing is difficult. While it is said that emeralds can be cleaned of most enhancements and refilled, identifying the original filler is key to its removal. Making it more difficult, some emeralds contain more than one filler. Don’t assume that because a stone is Colombian the filler is cedarwood oil.

Pricing. According to The Guide, fine-quality 2-ct. to 3-ct. emeralds are priced from $2,000 to $2,900 per carat. Extra-fine quality can top off at around $7,300 per carat, with a premium reserved only for Colombian gems. These prices reflect an assumption of a moderate amount of enhancement. Significant enhancement can decrease a stone’s value from 5% to 40%. Less enhancement, termed “slight,” can increase the value of a fine-quality emerald from 20% to 30%. For an extra-fine-quality emerald, a premium of 30% to 50% may be asked. Untreated fine-quality emerald will command at least 50% more per carat, and extra-fine unenhanced gems can command a premium exceeding 100% of the price per carat of a moderately enhanced gem.

Care and cleaning. Emeralds, like all beryls, have a hardness of 8 to 8.5 on the Mohs scale, which means they can take a fair amount of abuse and can’t be scratched by most objects. However, because many emeralds have fissures that make them vulnerable to breaking, one should be careful not to smack the stone against something hard.

As for cleaning, the debate goes on. Some dealers insist emeralds are inherently fragile and can be damaged by thermal shock from steam cleaners and even from the heat of an ultrasonic cleaner. Others who believe emeralds are not fragile, and who use the ExCel brand of enhancement, put emerald jewelry into the ultrasonic or under the steamer because they are convinced that the emerald and the enhancement will withstand the cleaning.

Bench precautions. If the enhancement can withstand the heat and chemicals used at the bench, then experts recommend simply being cautious about subjecting it to heat from the torch. Others are afraid to touch emeralds and won’t even set them into a simple prong mounting. In general, knowing where the enhancement and fissures are located can relieve a lot of stress for the bench jeweler.

Recommended reading. For more information, see “Gemstone Enhancement and Detection in the 1990s,” McClure and Smith, Gems & Gemology, GIA, Winter 2000; and Emerald and Other Beryls, John Sinkankas, Chilton Publishing, 1981.

Special thanks to Arthur Groom of Arthur Groom and Co., Ridgewood, N.J., and to Fernando Garzon at Clarity Enhancement Laboratories, New York.