GO 340 Gemstones & Gemology

Emporia State University

www.emporia.edu/earthsci/amber/go340/beryl.htm

Beryl

Emerald

Emerald is the deep green variety of beryl, an aluminum berylium silicate, Al2Be3(Si6O18). It is a cyclosilicate and often found in hexagonal primatic crystal forms. Beryl is 7.5-8 on the hardness scale and a vitreous luster. It has a conchoidal fracture and a brittle tenacity, which makes it sensitive to pressure and heat. Specific gravity is average to medium high, 2.66-2.87, and the refractive indices are 1.562-1.602. Although beryl may have an irregular distribution of color, the color is stable in light and heat. Asterism and cat's eye stones are possible. The best known variety of beryl is emerald, a deep green color. The green coloring agent is the impurity element, chromium, and possibly some vanadium. Some believe chromium defines emerald, whereas beryl colored with vanadium is merely green beryl. The finest emerald are transparent but more commonly they are clouded with inclusions. Dispersion is 0.014 and emerald has distinct pleochroim, showing blue-green and yellowish-green. It has no fluorescence but emerald shows bright red through the color or Chelsea filter.

Image taken from
Delta Bravo

Colombian green beryl.
Image taken from David
Barthelmy's Mineralogy
Database.

Occurrence and Mining

Emerald is found in a variety of geologic environments, from granite pegmatites to miarolitic cavities within granite. Alluvial placer or secondary deposits are not common because of beryl's average specific gravity. Beryl may be found also in volcanic rhyolites, metamorphic schist and greisens, which are formed hydrothermally or when mineralized water passes through fractures of granite. Colombian deposits are also hydrothermal in origin but the hot water passed through calcite rich rocks. Emerald crystals from the major three mines in Colombia are distinguished by their matrix rock (see esmerald.com for details).

Colombian emerald deposits are worked by hand, plucking gems from carbonaceous shale and from pegmatite veins of white and gray calcite. Unfortunately, only about one-third of these emeralds are worth cutting and it has been said over 70% is lost in the faceting process. Emerald mining in Colombia is detailed at gemtec.com and (esmerald.com).

Since the 1980s, Brazil became an important supplier and other noteworthy emerald deposits are in African nations (Zimbabwe, South Africa, Ghana, Madagascar, Malawi, Mozambique, Namibia, Nigeria, to name a few), Australia, India, Pakistan, and North Carolina in the U.S.A. For specific emerald localities visit mindat.org. Also, find out about Australian emerald go to Emerald - The Green Beryl Australia's Emerald Deposits by Grahame Brown, http://www.gem.org.au/emerald.htm.

Emerald Lore and Care

Emerald is the May birthstone and for the 20th and 35th anniversaries (Jewelry Central). Archaeologists have traced the origins and use of emerald back some 5000 years to Egypt and India. All green stones were referred to as emerald, with the name derived from Greek smaragdos which means green stone. Some famous emeralds include the 2205 carat "jug" in the Viennese treasury, cut from a single crystal (Schumann, 1997, p. 93). Historical legends and emerald lore may be found at emeraldstone.com and esmerald.com. Additional information on archaeolgical shipwreck finds for emerald can be found at http://www.adventures-inc.com/intro.html and http://www.adventures-inc.com/search.html, In Search Of Spanish Galleons: Cortes and the Isabella Emerald.

Emerald has a brittle tenacity and therefore it is imperative to never clean any beryl in an ultrasonic bath or steam cleaner! More care and handling tips are online (from emeraldstone.com), as well as some buying tips from Colombian dealers at gemtec.com and esmerald.com.


Brazilian emerald
in matrix. Image
taken from former
website Canelhas.

Image taken from
EmeraldStone.com

Faceting and Inclusions

Emeralds may be fashioned en cabochon or faceted, often in a step cut. One such step cut, called the emerald cut, was developed in the 17th century and this gemtec.com site has the faceting process detailed.

Inclusions are numerous in emerald. Excellent images can be found at gemtec.com and include unusual patterned inclusions; 3-phase inclusions; fingerprints, spirals, and calcite, quartz, and pyrite; as well as, tube inclusions.

Enhancements

Enhancements involve oiling and fracture filling to conceal defects. It has been suggested that 99% of all emeralds are enhanced with liquid or resin after cutting! Visit these sites for information on emerald enhancements, treatments, and Hughes' Catfights: Enhancement Codes and Trade Wars.

Synthetics and Imitations

The first synthetic emerald was created in 1848, but only recently have synthetic emeralds been on the market (formerly The Mineral and Gemstone Kingdom website). Synthetics often contain inclusions that may reveal their true identity (gemtec.com). Two of synthetic emerald producers are Chatham Created Gems and Tairus Created Emeralds (this site is only visible with Microsoft Explorer browser). General gem enhancement information can be found at Gem Hut enhancements.

Common assembled or composite stones, such as doublets, are difficult to detect when mounted (gemtec.com). They consist of two pale gems, such as rock crystal quartz, aquamarine, beryl, or pale emerald, cemented together with an deep green paste. The upper part or crown may be emerald and the pavilion, glass or synthetic spinel. If the composites are imitations of emerald, such as garnet, quartz, spinel, or glass, then they will show as green under the color filter.

Some of the synthetic and emerald imitations names include: Chatham Emerald and Gilson Emerald (all synthetics); Broghton Emerald, Endura Emerald, Mount St. Helens Emerald, Spanish Emerald (all four dyed green glass); African Emerald, South African Emerald, Traansvaal Emerald, Bohemian Emerald (all four fluorite); and other names, such as: Indian Emerald (dyed quartz or chalcedony), Night Emerald (peridot), Lithia Emerald (hiddenite), Congo Emerald (dioptase), Uralian Emerald (demantoid garnet), Emeraldite (green tourmaline).


For additional information, read an excerpts from the 2003 book Secrets of the gem trade (the connoisseur's guide to precious gemstones) by Richard Wise. The emerald chapter is reviewed at Ganoksin Jewelry Co., Ltd., http://www.ganoksin.com/borisat/nenam/rw-emerald.htm as well.


Beryl Photo Gallery

For more images of emerald visit the gemtec.com's emerald gallery. There are many more beryl varieties than emerald. Beryl is found in many colors, with each color assigned a varietal name.


Image taken from
The Image
The yellow to yellow-orange samples are referred to as golden beryl. This variety is not as expensive as aquamarine and is colored by iron (Fe+3).

Image taken from
The Image
The rarest beryl is the red variety, bixbite, which possibly owes its color to manganese (Mn+2). It is found in rhyolites of the mountains of Utah.
Image taken from
former Mineral
and Gemstone Kingdom

Image taken from
former Mineral
and Gemstone Kingdom
Peach colored beryl is called champagne beryl (left).

Green beryl, not emerald (right).



Image taken from
former Mineral
and Gemstone Kingdom

Image taken from
former Mineral
and Gemstone Kingdom
Heliodor is yellow-green to orange to brown, with orange and brown color due to manganese (Mn+2) and iron (Fe+3), while the yellow-green (not shown) is colored by uranium and is slightly radioactive (The Image).
Image taken from
former Mineral
and Gemstone Kingdom
Morganite (pink or described as salamon colored) is one of the more expensive beryls, although not as expensive as emerald. Morganite contains cesium and lithium, but the color is believed to be from a trace of manganese. It was named for a collector and American banker, J.P. Morgan.
Image taken from
former The Mineral
and Gemstone Kingdom

Image taken from
former The Mineral
and Gemstone Kingdom
Goshenite is colorless and and named after one locality at Goshen, Massachusetts in the US. It has been used to imitate diamond and emerald by applying silver or green metal foil to the pavilion (Schumann, 1997, p. 96). The final beryl variety is the blue to blue-green aquamarine.

Aquamarine

Aquamarine is the birthstone for March and the 19th anniversary stone. The name is derived from Latin, sea water, and is usually a medium blue with a green overtone. Aquamarine can be found in large, nearly flawless crystals, which is fortuitous because the clarity needs to be high for such a light colored gem. The color is caused by iron impurities (Fe+2), and heat treatment may be used to enhance the color. It is more expensive than blue topaz, but less expensive than emerald. Brazil produces exceptional aquamarine, although the gem is also found in Zambia, Mozambique, Angola, Nigeria, and Russia to name a few locations. For more information visit the International Colored Gemstone site, http://www.gemstone.org/gem-by-gem/english/aquamarine.html and Jewelry Central, http://www.jewelrycentral.com/Target_Aquamarine.asp.

A large Brazilian crystal was found in 1920, 19 inches long x 16 inches, weighing 243 pounds. The British Museum of Natural History owns an 879.5 carat flawless, step-cut aquamarine (CW Jewelers).


Image taken from
The Image


Image taken from
Amethyst Mineral Gallery

Image taken from
www.wilenskyminerals.com/
MINERAL_PHOTOS.html
,
image from Stuart Wilensky.
Retrieved 2003.

Image taken from
Amethyst Mineral Gallery

To learn more about emerald visit a website created by former GO 340 student Jacob Bray.

The material for this section came primarily from:

Return to the Syllabus or choose another gemstone below.

Alexandrite Amber Amethyst Chalcedony Diamond Emerald
Garnet Jade Malachite Opal Pearl Peridot
Ruby Sapphire Tanzanite Topaz Tourmaline Turquoise

This page originates from the Earth Science department for the use and benefit of students enrolled at Emporia State University. For more information contact the course instructor, S. W. Aber, e-mail: saber@emporia.edu Thanks for visiting! Webpage created: November 5, 2000; last update: March 9, 2008.

Copyright 1999-2008 Susan Ward Aber. All rights reserved.