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Encyclopedia > Emerald
Emerald

Emerald with host rock
General
Category Mineral
Chemical formula Beryllium aluminium silicate with chromium, Be3Al2(SiO3)6::Cr
Identification
Color Green
Crystal habit Hexagonal Crystals
Crystal system Hexagonal
Cleavage Poor Basal Cleavage (Seldom Visible)
Fracture Conchoidal
Mohs Scale hardness 7.5 - 8.0
Luster Vitreous
Refractive index 1.576 - 1.582
Pleochroism Distinct, Blue-Green/Yellow-Green
Streak White
Specific gravity 2.70 - 2.78

Emerald (Be3Al2(SiO3)6) is a variety of the mineral beryl, colored green by trace amounts of chromium and sometimes vanadium.[1] It is highly prized as a gemstone and by weight is the most valuable gemstone in the world, although it is often made less so by inclusions, which all emeralds have to some degree. Beryl has a hardness of 7.5 - 8 on the 10 point Mohs scale of hardness.[2] However, the effective hardness of an emerald is often reduced by fractures and inclusions. Most emeralds are highly included, so the toughness (resistance to breakage) is classified as generally poor. Image File history File linksMetadata Download high-resolution version (1057x1524, 483 KB) Specimen of emerald with attached host rock. ... Minerals are natural compounds formed through geological processes. ... This article does not cite its references or sources. ... General Name, Symbol, Number beryllium, Be, 4 Chemical series alkaline earth metals Group, Period, Block 2, 2, s Appearance white-gray metallic Standard atomic weight 9. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Standard atomic weight 26. ... In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. ... General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6, 4, d Appearance silvery metallic Standard atomic weight 51. ... In mineralogy, shape and size give rise to descriptive terms applied to the typical appearance, or habit of crystals. ... A crystal system is a category of space groups, which characterize symmetry of structures in three dimensions with translational symmetry in three directions, having a discrete symmetry group. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... For fractures in geologic formations, see Rock fracture. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... Pleochroism is an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90° angle to each other. ... The streak (also called powder color) of a mineral is the color of the powder produced when it is dragged across a unweathered surface. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... Minerals are natural compounds formed through geological processes. ... Three varieties of beryl: Morganite, Aquamarine, and Heliodor The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al2(SiO3)6. ... General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6, 4, d Appearance silvery metallic Standard atomic weight 51. ... General Name, Symbol, Number vanadium, V, 23 Chemical series transition metals Group, Period, Block 5, 4, d Appearance silver-grey metal Atomic mass 50. ... A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. ... In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation. ... In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ... The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. ... In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation. ...


Emeralds come in many shades of green and bluish green. There is a wide spectrum of clarity, dependent on the inclusions and fractures in the crystal. Clear stones with dark yet vibrant color command the highest prices.


Most emeralds are oiled as part of the post lapidary process, in order to improve their clarity. Cedar oil is often used, having a similar refractive index, and it is a generally accepted practice. The Federal Trade Commission requires the disclosure of this type of treatment when a treated emerald is sold.[3] The amount of oil entering an emerald microfissure is roughly equivalent to the size of a period (full stop) in print[citation needed]. The use of green tinted oil is generally not considered acceptable by the gem trade. A lapidary (the word means concerned with stones) is an artisan who practices the craft of working, forming and finishing stone, mineral, gemstones, and other suitably durable materials (amber, shell, jet, pearl, copal, coral, horn and bone, glass and other synthetics) into functional and/or decorative, even wearable, items (e. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... FTC headquarters, Washington, D.C. The Federal Trade Commission (or FTC) is an independent agency of the United States government, established in 1914 by the Federal Trade Commission Act. ... A full stop or period (sometimes stop, full point or dot), is the punctuation mark commonly placed at the end of several different types of sentences in English and several other languages. ...


Emeralds in antiquity were mined by the Egyptians and in Austria, as well as Swat in northern Pakistan.[4][5] PTDC Motel at Malam Jabba Ski Resort, Swat, NWFP, Pakistan. ...


A rare type of emerald known as a trapiche emerald is occasionally found in the mines of Colombia. A trapiche emerald exhibits a "star" pattern; it has raylike spokes of dark carbon impurities that give the emerald a six-pointed radial pattern. It is named for the trapiche, a grinding wheel used to process sugarcane in the region. Colombian emeralds are generally the most prized due to their transparency and fire. Some of the most rare emeralds come from three main emerald mining areas in Colombia: Muzo, Coscuez, and Chivor. Fine emeralds are also found in other countries, such as Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia. Species Saccharum arundinaceum Saccharum bengalense Saccharum edule Saccharum officinarum Saccharum procerum Saccharum ravennae Saccharum robustum Saccharum sinense Saccharum spontaneum Sugarcane or Sugar cane (Saccharum) is a genus of 6 to 37 species (depending on taxonomic interpretation) of tall grasses (family Poaceae, tribe Andropogoneae), native to warm temperate to tropical regions...


The value of an emerald depends on cut, color, clarity, and carat. The characteristics of Colombian emeralds set the highest standards of quality.[6]

Contents

Synthetic emerald

Emerald showing its hexagonal structure
Emerald showing its hexagonal structure

Emerald is a rare and valuable gemstone and, as such, it has provided the incentive for developing synthetic emeralds. 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 C. Chatham. Because Chatham's emeralds do not have any water and contain traces of vanadate, molybdenum and vanadium, a lithium vanadate flux process is probably involved. The other large producer of flux emeralds is Pierre Gilson Sr., which has been on the market since 1964. Gilson's emeralds are usually grown on natural colorless beryl seeds which become coated on both sides. Growth occurs at the rate of 1 mm per month and a typical seven-month growth run produces emerald crystals of 7 mm of thickness (Nassau, K. Gems Made By Man, 1980). Image File history File links Emerald. ... Image File history File links Emerald. ...


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 Inbruck, 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. Although not much is known about the original process, it is assumed that Leichleitner emeralds were grown on acid conditions. Later, from 1965 to 1970, the Linde Division of Union Carbide produced completely synthetic emeralds by hydrothermal synthesis. According to their patents (US3,567,642 and US3,567,643), 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 in order to prevent nucleation and confine growth to the seed crystals. Growth occurs by a diffusion-reaction process, assisted by convection. Typical growth conditions include pressures of 700-1400 bars at temperatures of 500 to 600°C with a temperature gradient of 10 to 25°C. Growth rates as fast as 1/3 mm per day can be attained[citation needed] Hydrothermal synthesis includes the various techniques of crystallizing substances from high-temperature aqueous solutions at high vapor pressures; also termed hydrothermal method. The term hydrothermal is of geologic origin. ... Tairus (Russian: Тайрус, a portmanteau of Тайско (Thai) and Русский (Russian)) is a synthetic gemstone manufacturer. ... Linde Logo The Linde Group is the international industrial gases company founded in 1879 and relaunched in September 2006, following the acquisition of The BOC Group by Linde AG. The group has major interests in industrial gases and plant engineering, and is currently headquartered in Wiesbaden, Germany. ... This article or section is incomplete and may require expansion and/or cleanup. ...


Luminescence in ultraviolet light is considered a supplementary test when making a natural vs. synthetic determination, as many, but not all, natural emeralds are inert to ultraviolet light. Many synthetics are also UV inert.[7] Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ...


Synthetic emeralds are often referred to as "created", as their chemical and gemological composition is the same as their natural counterparts. The Federal Trade Commission (FTC) has very strict regulations as to what can and what cannot be called "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."[8] FTC headquarters, Washington, D.C. The Federal Trade Commission (or FTC) is an independent agency of the United States government, established in 1914 by the Federal Trade Commission Act. ...


Today there are only four commercial laboratories growing synthetic emeralds, all of them are in Russia with one, Tairus, contributing to about 90% of world's production. Tairus (Russian: Тайрус, a portmanteau of Тайско (Thai) and Русский (Russian)) is a synthetic gemstone manufacturer. ...


Wispy veil-like inclusions are common in flux-grown synthetic emeralds.


Cultural and historical/mythical usage

The Gachala Emerald is one of the largest gem emeralds in the world at 858 carats. This stone was found in 1967 at La Vega de San Juan mine in Gachalá, Colombia. It is housed at the Smithsonian Institution in Washington DC.

Emerald is regarded as the traditional birthstone for May, as well as the traditional gemstone for the astrological signs of Taurus and Cancer. Image File history File linksMetadata Download high resolution version (818x1028, 219 KB) Summary The Gachala Emerald one of the largest Emeralds in the world at 858 carats. ... Image File history File linksMetadata Download high resolution version (818x1028, 219 KB) Summary The Gachala Emerald one of the largest Emeralds in the world at 858 carats. ... The Gachala Emerald, an uncut 5-cm emerald crystal weighing 858 carats, is named after the mining district where it was found in Colombia in 1967. ... The Smithsonian Institution Building or Castle on the National Mall serves as the Institutions headquarters. ... A birthstone is a gemstone or other semi-precious stone which is associated with a month of the Gregorian Calendar. ... This article or section does not adequately cite its references or sources. ... This article or section does not adequately cite its references or sources. ...


According to Rebbenu Bachya, the Hebrew word "Nofech" in Exodus 28:18 means "Emerald", and was the stone on the Ephod representing the tribe of Judah. According to other commentaries, "Nofech" means "garnet", and another stone, the "Bareqet", representing the tribe of Levi, is thought to be emerald. Not to be confused with Bahya ibn Paquda. ... “Hebrew” redirects here. ... It has been suggested that Pharaoh of the Exodus be merged into this article or section. ... The ephod (pronounced either ē´fod or ef´od) was one of eight ritual garments worn by the Israelite and later the Jewish High Priest while serving in the Jewish Temple in Jerusalem. ... The Tribe of Judah (Hebrew: יְהוּדָה, Praise; Standard Hebrew , Tiberian Hebrew ) is one of the Hebrew tribes, founded by Judah, son of Jacob(Israel). ... Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. ... In the Jewish tradition, a Levite (לוי Attached, Standard Hebrew Levi, Tiberian Hebrew Lēwî) is a member of the Hebrew tribe of Levi. ...


In some cultures, the emerald is the traditional gift for the 55th wedding anniversary. It is also used as a 20th and 35th wedding anniversary stone. A wedding anniversary is an anniversary which falls on the month and day a particular wedding took place, and which recurs every subsequent year. ...


Emeralds in culture

Emeralds, as with many rare valuable items, have been used as luck charms.


Famous emeralds

  • Gachala Emerald (origin: Colombia)
  • Chalk Emerald (origin: Colombia)
  • Nidvin Emerald (origin: Columbia)
  • Duke of Devonshire Emerald (origin: Colombia)
  • Mackay Emerald
  • Greenshorkire Emerald

The Gachala Emerald, an uncut 5-cm emerald crystal weighing 858 carats, is named after the mining district where it was found in Colombia in 1967. ... The Chalk Emerald is a 37. ...

Notes

  1. ^ Hurlbut, Cornelius S. Jr, & Kammerling, Robert C., 1991, Gemology, p. 203, John Wiley & Sons, New York
  2. ^ Hurlbut, Cornelius S. Jr, & Kammerling, Robert C., 1991, Gemology, p. 202, John Wiley & Sons, New York
  3. ^ http://www.ftc.gov/bcp/guides/jewel-gd.htm#%A7%2023.22%20Deception%20as%20to%20gemstones
  4. ^ Giuliani et al (2000): “Oxygen Isotopes and Emerald Trade Routes Since Antiquity.” Gaston Giuliani, Marc Chaudisson, Henri-Jean Schubnel, Daniel-H. Piat, Claire Rollion-Bard, Christian France-Lanord, Didier Giard, Daniel de Narvaez, Benjamin Rondeau. Science, January 28, 2000, pp. 631-633.
  5. ^ Giuliani et al (2000b): “La route des emeraudes anciennes.” Gaston Giuliani, Michèle Heuze, Marc Chaudisson. Pour la Science, November 2000, pp. 58-65.
  6. ^ http://micro.magnet.fsu.edu/birthstones/pages/emerald.html
  7. ^ Hurlbut, Cornelius S. Jr, & Kammerling, Robert C., 1991, Gemology, p. 81, John Wiley & Sons, New York
  8. ^ http://www.ftc.gov/bcp/guides/jewel-gd.htm#%A7%2023.23%20Misuse%20of%20the%20words%20%22ruby,%22%20%22sapphire,%22%20%22emerald,%22%20%22topaz,%22%20%22stone,%22%20%22birthstone,%22%20%22gemstone,%22%20etc.

References

  • Cooper, J.C. (Ed.) (1992). Brewer's Myth and Legend. New York: Cassell Publishers Ltd. ISBN 0-304-34084-7.
  • Sinkankas, John (1994). Emerald & Other Beryls. Geoscience Press. ISBN 0-8019-7114-4
  • Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20th ed.). New York: John Wiley and Sons. ISBN 0-471-80580-7
  • Weinstein, Michael (1958). The World of Jewel Stones. Sheriden House.
  • Nassau, Kurt (1980). Gems made by man. Gemological Institute of America. ISBN 0-87311-016-1
  • Ali, Saleem H. (2006). The Emerald City: Gemstone mining in Brazil[9]
  • World Bank: CASM Initiative[10]
  • [1]
  • http://www.mindat.org/min-1375.html
  • http://mineral.galleries.com/minerals/gemstone/emerald/emerald.htm
v  d  e
Gems and Crystals
Gems

Aquamarine · Emerald · Jasper · Lapis lazuli · Pearl · Peridot · Ruby · Sunstone · Tiger's eye GEM is an acronym for: Gas Electron Multiplier Gender Empowerment Measure Generalized Empirical Method — from Bernard Lonergan, also known as critical realism Genetically Engineered Microorganism Global Electric Motorcars Globally Executable MHP Goddard Earth Model — a model of the Earths gravity field Graphical Environment Manager — a windowing system created by... Quartz crystal Synthetic bismuth crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms, molecules... Aquamarine Aquamarine (Lat. ... Polished jasper pebble, one inch (2. ... A block of lapis lazuli Lapis lazuli is one of the oldest of all gems, with a history of use stretching back 7,000 years. ... Strand of akoya pearls from China Pearl farm, Seram, Indonesia A pearl is a hard, rounded object produced by certain animals, primarily mollusks such as oysters. ... Peridot (pronounced pear-uh-dot or pear-uh-doe, IPA: /pɛɹɪdɑːt/ or Fr. ... Ruby is a red gemstone. ... Sunstone, a feldspar exhibiting in certain directions a brilliant spangled appearance, which has led to its use as an ornamental stone. ... Polished tigers eye gemstone Tigers eye (also Tigers eye, Tiger eye) is a chatoyant gemstone that is usually yellow- to red-brown, with a silky luster. ...

Crystals

Agate · Amethyst · Chalcedony · Diamond · Pyrite · Quartz · Rhodochrosite · Sapphire · Topaz · Tourmaline Agate is a term applied not to a distinct mineral species, but to an aggregate of various forms of silica, chiefly chalcedony. ... Amethyst (SiO2) is a violet or purple variety of quartz often used as an ornament. ... Chalcedony knife, AD 1000-1200 Bloodstone redirects here. ... This article is about the gemstone. ... This article is about the mineral Pyrite or Fools Gold. ... Quartz is one of the most common minerals in the Earths continental crust. ... Rhodochrosite from Quirivilca, La Libertad, Peru. ... Sapphire (from Hebrew: ספּיר Sapir) is the single-crystal form of aluminium oxide (Al2O3), a mineral known as corundum. ... Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. ... The tourmaline mineral group is chemically one of the most complicated groups of silicate minerals. ...


  Results from FactBites:
 
Emerald - english (2007 words)
From a chemical-mineralogical point of view, emeralds are beryllium-aluminium-silicates with a good hardness of 7.5 to 8, and belong, like the light blue aquamarine, the tender pink morganite, the golden heliodor and the pale green beryl, to the large gemstone family of the beryls.
In the case of the emerald, it is mainly traces of chromium and vanadium which are responsible for the fascinating colour.
Emeralds are also cut in many other, mainly classical shapes, but if the raw material contains a large number of inclusions, it may often be cut into a gently rounded cabochon, or into one of the emerald beads which are so popular in India.
Emerald - Wikipedia, the free encyclopedia (945 words)
Emeralds in antiquity were mined by the Egyptians and in Austria as well as Swat in northern Pakistan.
A rare type of emerald known as a trapiche emerald is occasionally found in the mines of Colombia.
Emerald is regarded as the traditional birthstone for April and May, as well as the traditional gemstone for the astrological sign of Taurus.
  More results at FactBites »

 
 

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