Emerald is one of the three precious coloured gemstones, the most well-known variety of the family of Beryl, where other notable stones includes Aquamarine and Morganite. Emeralds are the deeper toned green variety of beryl, stones with a light tone are classified under Green Beryl instead. Emerald is one of the birthstones of May, named after the ancient Greek word 'smaragdus' for green. Cleopatra was known to be infatuated with Emeralds, and often used it in her royal adornments.
History & Lore
The biggest Emerald unearthed to date is the Bahia Emerald, weighing at 840 lbs, estimated to contain 180,000 cts of Emeralds that has been valued by experts at around USD$400 million. The largest faceted emerald is the Calgary, weighing in at 57,500 cts, it is valued at 1.15 million dollars. On the other hand, top quality Emeralds go for a tremendous price per carat such as the renowned Rockefeller Emerald. This top-quality piece went for USD$5.5 million on Christies Auction, purchased by Jewellery house Harry Winston, going for a record-breaking USD$305,000 per ct.
Emeralds have been a big part of religion in many empires and civilisations, such examples are the carved Mughal Emeralds as well as the world famous Emerald Buddha in Thailand.
Emerald colours range from yellow-green to blue-green. Tone plays a bigger part in Emeralds than other gemstones as a lower tone will define the gem as a Green Beryl instead of an Emerald, which differs greatly in value. The finest Emeralds hovers around 75% tone, with 0% being colourless and 100% being black.
In the trade, we use terms like Muzo Emerald and Muzo Green. These names come from the most famous Emerald mine in Colombia, the Muzo mine. Muzo Emeralds comes from the prestigious muzo mines, muzo green however is a term to describe a highly desired colour of Emerald which refers to a warm, grassy green with hints of yellow. Not all lababoratories use the trade term to describe colour. Laboratories such as SSEF only gives the colour and saturation level as a description and without trade names. Laboratories also have different systems of determining Emerald colours, thus a vivid green at one laboratory might not turn out to be a vivid green in another.
In terms of colour, the most highly valued colour is bluish-green. Bluish-green Emeralds from Colombia is rare as the mine mainly produces Emeralds with yellow tints instead. Bluish-green on the other hand is a common colour of Emeralds from Zambia. This makes Colombian bluish-green Emeralds must pricier as Colombia is also the preferred origin for Emeralds.
Most Emeralds are highly included, thus their toughness (resistance to breakage) is classified as fair. Due to the nature of having numerous inclusions and surface-breaking fissures, an eye-clean Emerald is generally considered to be flawless in clarity. Compared with many other gemstones, clarity plays a bigger part in Emeralds in determining the value of it.
Inclusions in Emeralds are sometimes a good sign that your Emeralds are more likely to be natural. That is because clean Emeralds are very rare, on most cases, an exceptionally clean Emerald could turn out to be a synthetic.
Emeralds comes from many origins, but the most desired and prominent remains to be the emeralds from Colombian mines. Finest quality Emeralds from Colombia may be even valued higher per carat than Diamonds of the same size. Another upcoming important source of Emeralds is Zambian mine which have a bluish overtone, and generally have better clarity than Colombian Emeralds.
Emeralds comes in many cuts but the most common will be Emerald cuts or ovals. More included stones are cut in cabochons which sometimes confused it with Jadeites.
Trapiche Emeralds are extremely rare. With a hexagonal core and a wheel like black inclusion as its signature appearance, it is highly sought after by collectors. Trapiche Emeralds are mostly cut into cabochons or tabs and are found mostly in Colombian Emeralds.
There is also a special phenomenon that is known as the Gota De Aceite effect, or also known as butterfly wing effect or oil drop effect. Emeralds with this effect exists maybe 1 in a 1000, mostly in the finest qualities. Characterised by an oily appearance, they are highly sought after by collectors and can go for extremely steep prices.
Emeralds are mostly treated with colourless oil, a treatment widely accepted in the industry in order to fill in surface-reaching cracks so that clarity and stability is improved. Emeralds are mostly oiled using cedarwood oil which has a similar refractive index, or other times with synthetic oil or polymers.
Usage of green tinted oil is unacceptable in the industry and such stones must be avoided. Emeralds are graded by the level of oil they go through, from None to Minor to Moderate to Significant, with some laboratories such as GRS grading from None to Insignificant to Minor to Moderate to Significant.
The lower the amount of oil present, the higher the value of the Emerald, with significant differences between oiled and non-oiled Emeralds. Moltenore recommends emeralds with a maximum of moderate oil present, with minor oil being a balance of affordability and quality.
A very important thing to note are synthetic Emeralds that widely exists in the market, produced through flux-grown or hydrothermal methods, these emeralds are chemically indifferent to natural Emeralds and hard to detect unless by the trained eye with appropriate equipment. This emphasizes the importance of purchasing Emeralds with certificates from accredited laboratories, such as Gubelin, SSEF, GIA, GRS.