Emerald

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Emerald
Beryl var. emeraude sur gangue (Muzo Mine Boyaca - Colombie) 2.jpg
Emerald crystal from Muzo, Colombia
General
Category Beryl variety
Formula
(repeating unit)
Be3Al2(SiO3)6
Crystal system Hexagonal (6/m 2/m 2/m) Space group: P6/mсc
Space group (6/m 2/m 2/m) – dihexagonal dipyramidal
Unit cell a = 9.21 Å, c = 9.19 Å; Z = 2
Identification
Formula mass 537.50
ColorGreen shades to colorless
Crystal habit Massive to well Crystalline
Cleavage Imperfect on the [0001]
Fracture Conchoidal
Mohs scale hardness7.5–8
Luster Vitreous
Streak White
Diaphaneity Transparent to opaque
Specific gravity Average 2.76
Optical propertiesUniaxial (−)
Refractive index nω = 1.564–1.595,
nε = 1.568–1.602
Birefringence δ = 0.0040–0.0070
Ultraviolet fluorescence None (some fracture-filling materials used to improve emerald's clarity do fluoresce, but the stone itself does not)
References [1]

Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium and sometimes vanadium. [2] Beryl has a hardness of 7.5–8 on the Mohs scale. [2] Most emeralds are highly included, [3] so their toughness (resistance to breakage) is classified as generally poor. Emerald is a cyclosilicate.

Gemstone Piece of mineral crystal used to make jewelry

A gemstone is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks and occasionally organic materials that are not minerals are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone.

Mineral Element or chemical compound that is normally crystalline and that has been formed as a result of geological processes

A mineral is, broadly speaking, a solid chemical compound that occurs naturally in pure form. A rock may consist of a single mineral, or may be an aggregate of two or more different minerals, spacially segregated into distinct phases. Compounds that occur only in living beings are usually excluded, but some minerals are often biogenic and/or are organic compounds in the sense of chemistry. Moreover, living beings often synthesize inorganic minerals that also occur in rocks.

Beryl gemstone: cyclosilicate

Beryl ( BERR-əl) is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring, hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red (the rarest), and white. Beryl is also an ore source of beryllium.

Contents

Etymology

The word "emerald" is derived (via Old French : esmeraude and Middle English : emeraude), from Vulgar Latin: esmaralda/esmaraldus, a variant of Latin smaragdus, which originated in Ancient Greek : σμάραγδος (smaragdos; "green gem"). [4]

Vulgar Latin Non-standard Latin variety spoken by the people of Ancient Rome

Vulgar Latin or Sermo Vulgaris, also Colloquial Latin, or Common Romance, was a range of non-standard sociolects of Latin spoken in the Mediterranean region during and after the classical period of the Roman Empire. Compared to Classical Latin, written documentation of Vulgar Latin appears less standardized.

Latin Indo-European language of the Italic family

Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets and ultimately from the Phoenician alphabet.

Properties determining value

Cut emeralds 5 Emeralds from Colombia.JPG
Cut emeralds

Emeralds, like all colored gemstones, are graded using four basic parameters–the four Cs of connoisseurship: color, clarity,cut and carat weight. Normally, in the grading of colored gemstones, color is by far the most important criterion. However, in the grading of emeralds, clarity is considered a close second. A fine emerald must possess not only a pure verdant green hue as described below, but also a high degree of transparency to be considered a top gem. [5]

Hue Property of a color indicating balance of color perceived by the normal human eye

Hue is one of the main properties of a color, defined technically, as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green, blue, and yellow",. Hue can typically be represented quantitatively by a single number, often corresponding to an angular position around a central or neutral point or axis on a colorspace coordinate diagram or color wheel, or by its dominant wavelength or that of its complementary color. The other color appearance parameters are colorfulness, saturation, lightness, and brightness.

Transparency and translucency property of an object or substance to transmit light with minimal scattering

In the field of optics, transparency is the physical property of allowing light to pass through the material without being scattered. On a macroscopic scale, the photons can be said to follow Snell's Law. Translucency is a superset of transparency: it allows light to pass through, but does not necessarily follow Snell's law; the photons can be scattered at either of the two interfaces, or internally, where there is a change in index of refraction. In other words, a translucent medium allows the transport of light while a transparent medium not only allows the transport of light but allows for image formation. Transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. The opposite property of translucency is opacity.

In the 1960s, the American jewelry industry changed the definition of emerald to include the green vanadium-bearing beryl. As a result, vanadium emeralds purchased as emeralds in the United States are not recognized as such in the UK and Europe. In America, the distinction between traditional emeralds and the new vanadium kind is often reflected in the use of terms such as "Colombian emerald". [6]

Color

In gemology, [7] color is divided into three components: hue , saturation , and tone . Emeralds occur in hues ranging from yellow-green to blue-green, with the primary hue necessarily being green. Yellow and blue are the normal secondary hues found in emeralds. Only gems that are medium to dark in tone are considered emeralds; light-toned gems are known instead by the species name green beryl. The finest emeralds are approximately 75% tone on a scale where 0% tone is colorless and 100% is opaque black. In addition, a fine emerald will be saturated and have a hue that is bright (vivid). Gray is the normal saturation modifier or mask found in emeralds; a grayish-green hue is a dull-green hue. [5]

Clarity

Brazilian emerald (grass-green variety of the mineral beryl) in a quartz-pegmatite matrix with typical hexagonal, prismatic crystals. Emerald in a quartz and pegmatite matrix.JPG
Brazilian emerald (grass-green variety of the mineral beryl) in a quartz-pegmatite matrix with typical hexagonal, prismatic crystals.

Emeralds tend to have numerous inclusions and surface breaking fissures. Unlike diamonds, where the loupe standard, i.e. 10× magnification, is used to grade clarity, emeralds are graded by eye. Thus, if an emerald has no visible inclusions to the eye (assuming normal visual acuity) it is considered flawless. Stones that lack surface breaking fissures are extremely rare and therefore almost all emeralds are treated ("oiled", see below) to enhance the apparent clarity. The inclusions and fissures within an emerald are sometime described as jardin (French for garden), because of their mossy appearance. [9] Imperfections are unique for each emerald and can be used to identify a particular stone. Eye-clean stones of a vivid primary green hue (as described above), with no more than 15% of any secondary hue or combination (either blue or yellow) of a medium-dark tone, command the highest prices. [5] The relative non-uniformity motivates the cutting of emeralds in cabochon form, rather than faceted shapes. Faceted emeralds are most commonly given an oval cut, or the signature emerald cut, a rectangular cut with facets around the top edge.

Loupe a small cylindrical or conical magnifying device without handle

A loupe is a simple, small magnification device used to see small details more closely. Unlike a magnifying glass, a loupe does not have an attached handle, and its focusing lens(es) are contained in an opaque cylinder or cone or fold into an enclosing housing that protects the lenses when not in use. Loupes are also called hand lenses.

Inclusion (mineral) inclusions in minerals

In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation.

A cabochon is a gemstone which has been shaped and polished as opposed to faceted. The resulting form is usually a convex (rounded) obverse with a flat reverse.

Treatments

Most emeralds are oiled as part of the post-lapidary process, in order to fill in surface-reaching cracks so that clarity and stability are improved. Cedar oil, having a similar refractive index, is often used in this widely adopted practice. Other liquids, including synthetic oils and polymers with refractive indexes close to that of emeralds, such as Opticon, are also used. These treatments are typically applied in a vacuum chamber under mild heat, to open the pores of the stone and allow the fracture-filling agent to be absorbed more effectively. [10] The U.S. Federal Trade Commission requires the disclosure of this treatment when an oil treated emerald is sold. [11] The use of oil is traditional and largely accepted by the gem trade, although oil treated emeralds are worth much less than un-treated emeralds of similar quality. Other treatments, for example the use of green-tinted oil, are not acceptable in the trade. [12] Gems are graded on a four-step scale; none, minor, moderate and highly enhanced. These categories reflect levels of enhancement, not clarity. A gem graded none on the enhancement scale may still exhibit visible inclusions. Laboratories apply these criteria differently. Some gemologists consider the mere presence of oil or polymers to constitute enhancement. Others may ignore traces of oil if the presence of the material does not improve the look of the gemstone. [13]

Emerald mines

A Colombian trapiche emerald Trapiche emerald (cropped).jpg
A Colombian trapiche emerald

Emeralds in antiquity were mined in Egypt at locations on Mount Smaragdus since 1500 BCE, and India, and Austria since at least the 14th century CE. [14] The Egyptian mines were exploited on an industrial scale by the Roman and Byzantine Empires, and later by Islamic conquerors. Mining ceased with the discovery of the Colombian deposits; only ruins remain. [15]

Colombia is by far the world's largest producer of emeralds, constituting 50–95% of the world production, with the number depending on the year, source and grade. [16] [17] [18] [19] Emerald production in Colombia has increased drastically in the last decade, increasing by 78% from 2000 to 2010. [20] The three main emerald mining areas in Colombia are Muzo, Coscuez, and Chivor. [21] Rare "trapiche" emeralds are found in Colombia, distinguished by ray-like spokes of dark impurities.

Zambia is the world's second biggest producer, with its Kafubu River area deposits (Kagem Mines) about 45 km (28 mi) southwest of Kitwe responsible for 20% of the world's production of gem-quality stones in 2004. [22] In the first half of 2011, the Kagem Mines produced 3.74 tons of emeralds.

Emeralds are found all over the world in countries such as Afghanistan, Australia, Austria, Brazil, [23] Bulgaria, Cambodia, Canada, China, Egypt, Ethiopia, France, Germany, India, Italy, Kazakhstan, Madagascar, Mozambique, Namibia, Nigeria, Norway, Pakistan, Russia, Somalia, South Africa, Spain, Switzerland, Tanzania, the United States, Zambia, and Zimbabwe. [1] In the US, emeralds have been found in Connecticut, Montana, Nevada, North Carolina, and South Carolina. [1] In Canada, in 1997 emeralds were discovered in the Yukon. [24]

Origin determinations

Since the onset of concerns regarding diamond origins, research has been conducted to determine if the mining location could be determined for an emerald already in circulation. Traditional research used qualitative guidelines such as an emerald’s color, style and quality of cutting, type of fracture filling, and the anthropological origins of the artifacts bearing the mineral to determine the emerald's mine location. More recent studies using energy dispersive X-ray spectroscopy methods have uncovered trace chemical element differences between emeralds; even emeralds mined within close proximity to one another. American gemologist David Cronin and his colleagues have extensively examined the chemical signatures of emeralds resulting from fluid dynamics and subtle precipitation mechanisms, and their research demonstrated the chemical homogeneity of emeralds from the same mining location and the statistical differences that exist between emeralds from different mining locations, including those between the three locations: Muzo, Coscuez, and Chivor, in Colombia, South America. [25]

Synthetic emerald

Emerald showing its hexagonal structure Emerald.png
Emerald showing its hexagonal structure

Both hydrothermal and flux-growth synthetics have been produced, and a method has been developed for producing an emerald overgrowth on colorless beryl. The first commercially successful emerald synthesis process was that of Carroll Chatham, likely involving a lithium vanadate flux process, as Chatham's emeralds do not have any water and contain traces of vanadate, molybdenum and vanadium. [26] The other large producer of flux emeralds was Pierre Gilson Sr., whose products have been on the market since 1964. Gilson's emeralds are usually grown on natural colorless beryl seeds, which are coated on both sides. Growth occurs at the rate of 1 mm per month, a typical seven-month growth run produces emerald crystals 7 mm thick. [27]

Hydrothermal synthetic emeralds have been attributed to IG Farben, Nacken, Tairus, and others, but the first satisfactory commercial product was that of Johann Lechleitner of Innsbruck, Austria, which appeared on the market in the 1960s. These stones were initially sold under the names "Emerita" and "Symeralds", and they were grown as a thin layer of emerald on top of natural colorless beryl stones. Later, from 1965 to 1970, the Linde Division of Union Carbide produced completely synthetic emeralds by hydrothermal synthesis. According to their patents (attributable to E.M. Flanigen), [28] acidic conditions are essential to prevent the chromium (which is used as the colorant) from precipitating. Also, it is important that the silicon-containing nutrient be kept away from the other ingredients to prevent nucleation and confine growth to the seed crystals. Growth occurs by a diffusion-reaction process, assisted by convection. The largest producer of hydrothermal emeralds today is Tairus, which has succeeded in synthesizing emeralds with chemical composition similar to emeralds in alkaline deposits in Colombia, and whose products are thus known as “Colombian created emeralds” or “Tairus created emeralds”. [29] Luminescence in ultraviolet light is considered a supplementary test when making a natural versus synthetic determination, as many, but not all, natural emeralds are inert to ultraviolet light. Many synthetics are also UV inert. [30]

Emerald made by hydrothermal synthesis SyntEmerald 0302.jpg
Emerald made by hydrothermal synthesis

Synthetic emeralds are often referred to as "created", as their chemical and gemological composition is the same as their natural counterparts. The U.S. Federal Trade Commission (FTC) has very strict regulations as to what can and what cannot be called a "synthetic" stone. The FTC says: "§ 23.23(c) It is unfair or deceptive to use the word "laboratory-grown", "laboratory-created", "[manufacturer name]-created", or "synthetic" with the name of any natural stone to describe any industry product unless such industry product has essentially the same optical, physical, and chemical properties as the stone named." [11]

In culture and lore

Emerald is regarded as the traditional birthstone for May as well as the traditional gemstone for the astrological signs of Cancer. [31]

One of the quainter anecdotes about emeralds was told by the 16th-century historian Brantôme, who referred to the many impressive emeralds the Spanish under Cortez had brought back to Europe from Latin America. On one of Cortez's most notable emeralds he had the text engraved, Inter Natos Mulierum non sur-rexit mayor ("Among those born of woman there hath not arisen a greater," Matthew 11:11) which referred to John the Baptist. Brantôme considered engraving such a beautiful and simple product of nature sacrilegious and considered this act the cause for Cortez's loss of an extremely precious pearl (to which he dedicated a work, A beautiful and incomparable pearl), and even for the death of King Charles IX of France, who died soon afterward. [32]

The chief deity of one of India's most famous temple, the Meenakshi Amman Temple in Madurai, is the goddess Meenakshi, whose idol is traditionally thought to be made of emerald. [33]

Notable emeralds

EmeraldOriginSizeLocation
Bahia Emerald [34] Brazil, 2001180,000 carats, crystals in host rockLos Angeles County Sheriff's Department [35]
Carolina Emperor [36] [37] United States, 2009310 carats uncut, 64.8 carats cut North Carolina Museum of Natural Sciences, Raleigh
Chalk Emerald Colombia38.40 carats cut, then recut to 37.82 carats National Museum of Natural History, Washington
Duke of Devonshire Emerald Colombia, before 18311,383.93 carats uncut Natural History Museum, London
Emerald of Saint Louis [38] Austria, probably Habachtal51.60 carats cut National Museum of Natural History, Paris
Gachalá Emerald [39] Colombia, 1967858 carats uncut National Museum of Natural History, Washington
Mogul Mughal Emerald Colombia, 1107 A.H. (1695-1696 AD)217.80 carats cut Museum of Islamic Art, Doha, Qatar
Patricia Emerald [40] Colombia, 1920632 carats uncut, dihexagonal (12 sided) American Museum of Natural History, New York
Mim Emerald [41] Colombia, 20141,390 carats uncut, dihexagonal (12 sided) Mim Museum, Beirut

See also

Related Research Articles

Amethyst Mineral, quartz variety

Amethyst is a violet variety of quartz.

Sapphire gemstone

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, copper, or magnesium. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. The only color corundum stone that the term sapphire is not used for is red, which is called a ruby. Pink colored corundum may be either classified as ruby or sapphire depending on locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs).

Ruby variety of corundum, mineral, gemstone

A ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, together with amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium.

Chrysoberyl oxide mineral

The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula BeAl2O4. The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones, although they both contain beryllium. Chrysoberyl is the third-hardest frequently encountered natural gemstone and lies at 8.5 on the Mohs scale of mineral hardness, between corundum (9) and topaz (8).

Gemology Science dealing with natural and artificial gemstone materials

Gemology or gemmology is the science dealing with natural and artificial gemstone materials. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems.

Tanzanite Blue to purple variety of the mineral zoisite

Tanzanite is the blue and violet variety of the mineral zoisite, caused by small amounts of vanadium, belonging to the epidote group. Tanzanite is only found in Tanzania, in a very small mining area near the Merelani Hills.

Tsavorite

Tsavorite or tsavolite is a variety of the garnet group species grossular, a calcium-aluminium garnet with the formula Ca3Al2Si3O12. Trace amounts of vanadium or chromium provide the green color.

Demantoid green andradite variety

Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.

Gemological Institute of America research institute in Carlsbad, California

The Gemological Institute of America, or GIA, is a nonprofit institute dedicated to research and education in the field of gemology and the jewelry arts. Founded in 1931, GIA's mission is to protect all buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality. The institute does so through research, gem identification and diamond grading services and a variety of educational programs. Through its world-renowned library and subject experts, GIA acts as a resource of gem and jewelry information for the trade, the public and worldwide media outlets.

Tairus


Tairus is a synthetic gemstone manufacturer. It was formed in 1989 as part of Mikhail Gorbachev's perestroika initiative to establish a joint venture between the Russian Academy of Sciences and Tairus Created Gems Co Ltd. of Bangkok, Thailand. Today Tairus is a major supplier of hydrothermally grown gemstones to the jewellery industry. Later, Tairus became a privately held enterprise, operating out of its Bangkok distribution hub under the trade name Tairus, owned by Tairus Created Gems Co Ltd. of Bangkok, Thailand.

Gachalá Emerald one of the largest emeralds in the world

The Gachalá Emerald, one of the most valuable and famous emeralds in the world, was found in the year 1967, in the mine called Vega de San Juan, located in Gachala, a town in Colombia, located 142 km (88 mi) from Bogota. Gachalá Chibcha means "place of Gacha." Presently the emerald is in the United States, where it was donated to the Smithsonian Institution by the New York City jeweler, Harry Winston.

In gemmology, a Chelsea filter is a dichromatic optical filter used for identifying coloured stones.

Diamond (gemstone) type of gemstone

A diamond is one of the best-known and most sought-after gemstones. Diamonds have been used as decorative items since ancient times; some of the earliest references can be traced to 25,000 - 30,000 B.C.

Ammolite

Ammolite is an opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral contained in nacre, with a microstructure inherited from the shell. It is one of few biogenic gemstones; others include amber and pearl.1 In 1981, ammolite was given official gemstone status by the World Jewellery Confederation (CIBJO), the same year commercial mining of ammolite began. It was designated the official gemstone of the City of Lethbridge, Alberta in 2007.

Kelsey Lake Diamond Mine

Kelsey Lake Diamond Mine is a defunct diamond mine in Colorado, USA. It is located in the State Line Kimberlite District, near the Wyoming border, and consists of nine kimberlite volcanic pipes, of which two were open pit mined.

Ronald Ringsrud gemologist

Ronald Ringsrud is an emerald dealer and writer of the book Emeralds, A Passionate Guide. This work draws on Ringsurd's decades of work in the emerald industry and includes a foreword written by John Koivula, the Chief Gemologist at GIA.

Colombian emeralds

Emeralds are green precious gemstones that are mined in various geological settings. They are minerals in the beryl group of silicates. For more than 4,000 years, emeralds have been among the most valuable of all jewels on Earth. Colombia, located on the continent of South America, is the country that mines and produces the most emeralds for the global market. It is estimated that Colombia accounts for 70-90% of the world's emerald market. While commercial grade emeralds are quite plentiful, fine and extra fine quality emeralds are extremely rare. Colombian emeralds over 50 carat can cost much more than diamonds of the same size.

Blue diamond is a type of diamond which exhibits all of the same inherent properties of the mineral except with the additional element of blue color in the stone. They are colored blue by trace amounts of boron that contaminate the crystalline lattice structure. Blue diamonds belong to a subcategory of diamonds called fancy color diamonds, the generic name for diamonds that exhibit intense color. Blue diamonds range in grade from Flawless to Included, just as in the case of white diamonds.

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Further reading