Gemstones: Emerald (Beryl)
Emerald Gemstones
Source: Afghanistan, Brazil, Canada (Regal Ridge), Columbia, Madagascar, Pakistan, Zambia
Birthstone: May
The name "Emerald" (Émeraude French, Smaragd German, Esmeralda Spanish) comes from the Greek word smaragdos; a name that was given to several gemstone minerals having little in common chemically, but sharing a similar bluish-green color. An emerald is a form of Beryl, a mineral group that includes aquamarine and Morganite. Emerald's leaf-green color is partially due to allochromatic coloration from trace amounts of chromium (Cr) and vanadium (V) impurities.
Emerald is transparent to translucent member of the beryl family of minerals (aquamarine, morganite, goshenite, red beryl), and is typically associated with igneous rock. Emerald is a cyclosilicate of beryllium and aluminium, and owes its green color to chromium and vanadium, along with other trace coloring agents which include beryllium (berillium) (Be) aluminum silicate and iron (Fe).
Many varieties of emerald have a leaf-green to yellowish-green hue, but Columbian emeralds have a particularly intense greenish hue with a bluish-green overtones, which makes their color very difficult to capture in photographic images.
Emerald Inclusions - Jardin
Emerald is one of the most difficult gemstones to cut because of the many fluid inclusions found in rough crystals which can make them very brittle. These multiphase inclusions are like fingerprints and can reveal the geographic location of their origin. The French refer to the large number of inclusions in the stone as "jardin," or "garden," because they can resemble plant foliage. These inclusions can be two-phase tubes that run parallel to the c-axis, or two to three-phase secondary healed fractures or basal cleavages.
Emeralds with many inclusions should be treated with care and be protected from direct blows to the stone. Oils are commonly used to fill-in the fissures (see "emerald enhancements" below). The extreme rarity of transparent, inclusion-free emeralds can make them more valuable than diamonds.
Emerald (Beryl) Crystallography, Chemistry, Physical Properties
Emerald (Beryl) Optical Properties
Ancient Egyptian Emerald Mining
The ancient Egyptian, Babylonian, Roman and Byzantine cultures obtained their emeralds from the Sikair-Zubara (Sikait-Zabara) region in the eastern part of Upper Egypt, near the Red Sea town of Berenice. This emerald-mining region became known as the Mons Smaragdus or 'Emerald Mountains" and after the conquest of Alexander the Great, and was also referred to as the "Cleopatra Mines" in latter years.
Cleopatra Mines in Egypt (Photo: Public Domain) |
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Sikair-Zubara (Photo: Public Domain) |
The Egyptian mines may have been worked as early as 1800 BC, but most likely were at peak production during the Ptolemaic period from 330 BC to 30 BC. The first mines to be re-discovered were at Gebel Zabara, uncovered on an expidition by French mineralogist F. Cailliaud, in 1816. Sikait was identified two years later. The Wadi Gimal and Wadi Sikait mines are adjacent to the ancient roman mining villages of Nugrus and Sikkait.
Indian Emerald Mining
Indian emeralds, with their distinct bluish hue, were found near Ajmer and Udaipur in north-western Rajasthan State. The Mughals of India, including the builder of the Taj Mahal, Shah Jahan, loved emeralds so much they inscribed them with sacred text and wore them as talismans. These sacred stones were called Mughal emeralds.
One of the largest emeralds ever recorded was the 218 carat tablet-cut rectangular "Mogul Emerald," possibly belonging to the last great Mogul ruler of India, Emperor Aurangzeb from the late 1600s.
Canadian Emerald
Canadian emeralds were first discovered in 1998, in the 'Regal Ridge' area of the Yukon. Confirmation of the find at the University of British Columbia (UBC) created a 'emerald rush' to the area by several prominent mining companies. The first emeralds were found by Bill Wengzynowski, a prospector for Expatriate Resources in Vancouver.
Although the color of the stones is considered to be exceptional, it is yet to been determined if mining in the area will be commercially feasible. In 2003 preliminary exploration of Regal Ridge was begun by True North Gems Inc., who is also investigating areas of Ontario. The Yukon property is now known as "Tsa da Glisza," located in the Finlayson mining district of the Yukon Territory, Canada. Tsa da Glisza is situated on a high alpine ridge of the Pelly Mountain range.
On To:
Colombian Muzo, Chivor & Trapiché Emeralds
Afghanistan's Emeralds from the Panjshir Valley
Madagascar's Emeralds from Kianjavato
Brazilian Emeralds from Minas Gerais
Emerald Enhancements & Treatments
Clarity enhancement and surface treatment of emeralds using glycerin, Canada balsam oil, cedarwood oil or clove oil impregnation is practiced universally. The only way to confirm that an emerald hasn't been oil treated is if the cut stone has no fractures at the surface for oil to enter into the stone. If an emerald is cleaned in an ultrasonic or steam cleaner the oil can leach out of the fractures. This will make the surfacing inclusions appear more obvious. If this occurs, the emerald can be re-oiled to fill in the fractures. Fractures can also be filled with Opticon Fracture Sealer which is an epoxy resin.
Due to the typically high amount of inclusions within the stone, emerald has a lower durability than other varieties of beryl such as aquamarine. When an emerald is set in a ring with a prong setting extra care should be used.
Emerald Simulants & Soude Emerald
Simulated emeralds (simulants) made of glass or quartz are doublets or triplets with a transparent layer of green gelatin sandwiched between. These simulants are known as "soude emerald." A Chelsea Filter is used to differentiate and identify natural emeralds from simulants by isolating the chromium found in real emeralds, although some older soude emeralds may appear as red or pink.
Synthetic Emerald
Synthetic emerald was developed by Caltech graduate, Carroll Chatham in 1939. Synthetic emerald is created using the Flux-Growth, and Lechleitner Synthetic Overgrowth (hydro-thermal) methods and is sold under the trade names Chatham Created Gems and Gilson. Synthetic emerald can be identified by its characteristic inclusions. Initially, the only way to distinguish a Chatham emerald from a natural emerald was to heat the stone to the point where the natural stone would shatter due to moisture contained within the inclusions. Synthetic Emerald has a refractive index of 1.561.
Further Reference: The Gemstone Inclusion Library - Emerald
Bibliography on Emeralds
1. Colombian Emeralds - by Gemologist Edna B. Anthony  . www.attawaygems.com
2. Colombian Emeralds - Ronald Ringsrud Co. . www.emeraldmine.com
3. The Mineralogical Record - A Mineral Collector's Knowledge Database. www.minrec.org
4. Afghanistan Geological Survey . www.bgs.ac.uk
5. AGTA - Trapiché Emeralds . www.agta-gtc.org
6. True North Gems Inc. . www.truenorthgems.com
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