Emerald The green variety of Beryl, the mineral group that contains Emerald, Aquamarine, Heliodore, Morganite, and Goshenite.

History

Classification and Grading

Characteristics of Emerald

Evaluation

Treatments and Enhancements

Buying an Emerald, Things to Consider

Bibliography

History

Emeralds have been highly prized and valued as a gemstone since early times. Of all the  members of the Beryl family of minerals, the Emerald is considered the most valuable. From the Greek, smaragdos and the Latin beryllus and emaraude, the name Emerald was first coined in the sixteenth century.

In ancient times, Emerald was associated with the goddess Venus and endowed with the power to show faithfulness in one's partner. The Romans brought medicinal connotations to Emerald and associated it restoring sight and soothing weary eyes. Over the centuries, all sorts of mystical powers have been attributed to the Emerald including the power of prescience, to attract wealth, and ward off epilepsy.

The two most important historical Emeralds are the 1,384 carat Devonshire Emerald and the 630 carat Patricia Emerald displayed by the American Museum of Natural History in New York.

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Classification and Grading

Emerald can be defined as opaque, translucent or transparent Beryl with medium to dark tones of green in color. Beryl that is light or very light in tone are more properly called Green Beryl.

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

• Colombian Emerald - The finest qualities have traditionally been called Colombian after their country of origin. These fine grades are characterized by the deep, intense pure green with either yellow or blue undertones.
• Siberian or Russian Emerald - From the Ural mountains these stones are lighter and more yellow than Colombian stones.
• African Emerald - In some cases the color of these stones rivals fine Colombian but more commonly are characterized by blue and gray overtones.

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Characteristics of Emerald

• Chemical Composition - Beryllium Aluminum Silicate, Be₃Al₂(SiO₃)₆.
• Crystallography - Hexagonal System with prismatic habit.
• Hardness - 8 on the Moh's Hardness Table
• Cleavage - Very difficult
• Fracture - Conchoidal, brittle
• Characteristic inclusions - Calcite and pyrite are common included materials in Emerald. Three phase inclusions (cavity containing a solid, liquid and gas) are sometimes seen.
• Fluorescence - Weak orange or violet red

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Evaluation

Emerald of high quality is characterized by an intense green color with undertones of yellow or blue. Imperfections are common and expected in Emerald. Finer stones usually display an even distribution of small imperfections. This distribution, termed 'jardin' from the French for garden, results in a glowing appearance to the stone.

Color is the most important characteristic when evaluating Emerald. Fine stones have an intensity of green and an evenness of color with a minimum of striation or banding. The lack of surface imperfections, quality of final polish and symmetry are also important in the overall evaluation.

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Treatments and Enhancements

The most common treatments and enhancements of Emerald are:

• Oiling - A common practice, rough stone is treated with green colored oil which impregnates the fine structures of the surface of the Emerald. This treatment is not permanent.
• Dyes, laminates and impregnated waxes - sometimes seen but are not permanent and should be avoided.

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Buying an Emerald, Things to Consider
 

There are three elements that should be considered when buying an Emerald.

Color - Look for a deep, intense pure green color with undertones of yellow or blue. 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. Imperfections should be small and evenly distributed resulting in the desirable 'jardin' glow.

Cut - Emeralds, are usually cut in a fashion that provides for enough body mass to display depth of color. The Emerald Cut, for example provides a large face with substantial body mass. Attention to final finish and facet symmetry is recommended.

Emerald has always been a desirable gemstone. In finer qualities, prices have increased dramatically over the last few years with supply diminishing. Gem grade stones today can command per carat prices that are comparable to Diamond prices.

Emerald can be safely used in all types of jewelry including rings and bracelets. Although hard, it can be brittle. Care should be taken when wearing Emerald rings or bracelets. Ultrasound cleaning should not be used with Emerald jewelry and heat should never be applied.

Bibliography

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