Lush green is the color of spring – and May’s birthstone, emerald

Written by Lorraine Hornby

With its lush deep-green color, symbolic of spring, emerald is an apt birthstone for the month of May. It is part of the beryl gem species (the blue-green variety of beryl is aquamarine, the March birthstone). This emerald crystal is from the Muzo mine in Columbia.

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Submitted photo/Wikimedia

Emerald crystal, Muzo mine

The oldest known emeralds are from South Africa, and scientists have determined that they were formed nearly three billion years ago, according to the GIA (Gemological Institute of America). The oldest emerald mines were in Egypt, and Cleopatra prized emeralds in her royal jewelry.

European appreciation of emeralds began after Spanish explorers invaded South America, where the Incas had already been using emeralds in jewelry and religious ceremonies for hundreds of years.

Random Emerald Trivia

One of the most sacred treasures in the Grand Palace in Bangkok, Thailand is the Emerald Buddha. Which is not, in fact emerald – it is jadeite. But its name reflects the ubiquitous use of the term emerald to describe a deep green color rather than a specific gemstone.

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Photo courtesy The Longest Way Home

Emerald Buddha

Although emeralds are rated at 7.5 to 8 on the Moh’s hardness scale (which ranges from 1 to 10 – diamonds have a 10 rating), they are sensitive to knocks. A special step-cut, in which the corners are truncated rather than pointed, is known in the jewelry world as an “emerald cut” (although it is also used on gemstones other than emeralds). The photo below shows a classic emerald cut. It also shows a stone that has many inclusions, a common issue with emeralds and one which makes the stone less valuable.

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Submitted photo

Emerald cut

The Bahia Emerald, discovered in Columbia in 2001, contains the largest single emerald crystal ever found. The rock is embedded with numerous very large emerald crystals, and weighs approximately 800 pounds. It has been the subject of ownership disputes and legal action almost since its discovery, and the court cases surrounding the Bahia Emerald have become as famous as the gem itself. It is currently under lock and key in the possession of the Los Angeles County Sheriff’s Department until the courts determine who really owns it.

Where emeralds are found

Columbia is one of the most important sources for quality emeralds. Other significant deposits are in Brazil, South Africa, and Zimbabwe.


Because emeralds are often cloudy and [have inclusions], it has become a common practice to treat them with a process known as “oiling” to improve color, clarity and stability. The gems are immersed in a colorless oil or resin, which seeps into fissures in the gems and enhances the appearance of the stone. Legally, such treatments must be disclosed to the consumer. If an emerald that has been oiled is put in an ultrasonic or steam cleaner (which are common methods of cleaning jewelry), it could remove the oils and a visibly different gem emerges. It is possible, however, to re-oil the stone. 

Synthetic emeralds

Since about the 1950s, very high quality synthetic emeralds have been available. The Chatham Company pioneered the process for lab-grown emeralds (and a short list of other desirable gemstones), so if you come across a “chatham emerald” you know that it is a man-made gemstone.

Lorraine Hornby is a local jewelry artist and Certified Gemologist, SCC. Her work can be viewed at, and you can read more about gemstones and jewelry fabrication on her blog,

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