emerald

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emerald
Émeraude, calcite 300.4.1981.jpg
Emerald crystal on calcite from Muzo , Boyacá Department, Colombia
General and classification
chemical formula Al 2 Be 3 [Si 6 O 18 ], admixture of Cr 3+ and V ions
Mineral class
(and possibly department) 		see beryl
Similar minerals Demantoid , Diopside , Dioptas , Grossular , Green Tourmaline
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Physical Properties
Mohs hardness 7.5 to 8
Density (g / cm 3 ) 2.6 to 2.8
Cleavage indistinct
Break ; Tenacity shell-like
colour dark to light green
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.568 to 1.602
n ε  = 1.564 to 1.595
Birefringence δ = 0.004 to 0.007
Optical character uniaxial negative
Pleochroism natural: green-blue-blue-green to yellow-green; synthetic: yellow-green-blue-green
Other properties
Special features many inclusions and cracks

Emerald is a variety of the hexagonal crystal system crystallizing silicate - Minerals beryl and has a Mohs hardness of 7.5 to 8. Its chemical composition is characterized by Al 2 Be 3 [Si 6 O 18 , above]. The color is green due to the admixture of chromium and vanadium ions, the line color is white.

Etymology and history

The word "emerald" was derived from the Latin . smaragdus borrowed from the Greek σμάραγδος, smáragdos (green stone) and is related to Sanskrit marakatam (green); however, the word is probably of Semitic origin, cf. akkad. barraqtu "shiny stone", at the root BRQ "shine" and Heb . ברקת ( bāreqet ), "emerald" to ברק ( bâraq ), "to flash".

Emerald mining began in ancient Egypt . As early as the 13th century BC The gemstones were mined there; the mines of Sikait and Sabara supplied Europe with the precious minerals for more than a thousand years. The stones were also in great demand in the Orient with the Persians , Ottomans and the Mughal rulers of India . When the Spaniards conquered South America in the 16th century , they also encountered a brisk trade in stones there, which reached from Colombia as far as Chile and Mexico . The Muzo mine, captured by them in 1573, replaced the Egyptian sources from then on. 55 percent of all emeralds worldwide come from Colombia today.

In 1935, IG Farben in Bitterfeld was the first to succeed in producing synthetic emeralds in grindable quality. They were sold for advertising purposes under the name Igmerald , a made-up word from IG and the English word emerald for emerald.

Varieties

A trapiche emerald from the Muzo mine, Colombia

Inclusions in emeralds are normal and are called jardin . In contrast to diamonds , inclusions do not reduce the price if they do not appear disruptive. They rather serve as a criterion for distinguishing between synthetic stones.

  • Trapiche emerald , a rare variety in the shape of a wagon wheel with six spokes (not a twin), created through inclusions and special growth processes, mainly from Colombia
  • Emerald cat's eye , with a cat's eye effect

Education and Locations

Emeralds are found in pegmatite veins, especially in granites , but also in metamorphic rocks such as gneiss and as mineral soap in river sediments. The crystals are seldom larger than a few centimeters and their quality is usually impaired by cracks, inclusions (often biotite and other mica or liquids) and admixtures of other minerals. Their occurrence is linked to tectonic fault zones.

Important deposits can be found in Colombia , Brazil and the Ural Mountains . Smaller occurrences can be found in southern Africa. The only sites of relevance in Europe are in the Habach Valley in Austria ( Habach Valley Emerald Mine ) and at Byrud Gård in Viken , Norway. In the past, emeralds were mined there. There is also an Egyptian origin for antiquity.

Use as a gem stone

Ointment vessel by Dionysio Miseroni , exhibited in the Vienna Treasury
Five emeralds in the so-called "emerald cut"

Emeralds were and are valued by many cultures around the world as particularly valuable jewelery and precious stones. Emeralds from Brazil in particular can achieve higher prices than a diamond of the same size due to their strong green.

The preferred type of cut in clear emerald crystals is the eponymous "emerald cut", an octagonal step cut, which was developed with regard to the impact sensitivity of the stone.

Big and famous emeralds

Surname Weight
in carats 		Found year Found land comment
Teodora ( God's gift ) 57,500 (11.5 kg) Brazilian mine without further details Honed in India. The stone was offered at an auction in Canada in 2012, but could not be bought because the authenticity of the stone was in doubt due to the arrest of the current owner on multiple suspicions of fraud.
No individual name known 34,000 (6.8 kg) 2009 From a river soap in Madagascar The crystal has so far only been presented to the public twice - once in Tucson, in 2010, and in Munich, at “Inhorgenta 2012”. Total length: 150 mm, width: 145 mm.
No individual name known 16,300 Exhibited in the Topkapi Serail Museum in Istanbul
For a 11,000 (≈ 2.27 kg) 1999 Muzo , Boyacá Province, Colombia Owned by the Coexminas company
Elephant (elephant) 6,225 (≈ 1.3 kg) 2010 Gemfields, Zambia
Inkalamu (lion) 5,655 (≈ 1.1 kg) 2018 Gemfields, Zambia
No individual name known 2,205 1641 Colombia 10 cm high ointment vessel by Dionysio Miseroni; exhibited in the Vienna Treasury
Devonshire emerald over 1,350 Muzo Mine, Colombia Owned by the Duke of Devonshire
Gachalá emerald 858 1967 Vega de San Juan mine, Colombia Issued at the Smithsonian Institution
Patricia 632 1920s Chivor, Colombia Named after the mine owner's daughter, exhibited in the American Museum of Natural History
Mughal emerald 217.80 1695 The stone bears engraved prayer texts on one side and floral ornaments on the other, it is privately owned.
Star of Atocha 12.72 1620s Colombia Once valued at $ 3.2 million to $ 5 million. Part of the cargo of the Nuestra Señora de Atocha, galleon en route to Spain, sunk on September 5, 1622.

The largest uncut stone is the Bahia Smaragd, a coherent group of intensely colored crystals that was found in 2011 in Pindobacu in the Brazilian state of Bahia , weighing 1.9 million carats (= 381 kg)

Economical meaning

Emerald deposits are an economic factor that should not be underestimated. Most of the producing countries export the stones. In Colombia, emeralds are exported annually with an official trade volume of between 150 and 400 million US dollars, although it is estimated that the same amount must be added for the black market.

Manipulations and imitations

Emerald is very insensitive in its optical properties (color, luster), it only changes its color at around 700 to 800 ° C, but it often shows an uneven color distribution and, due to many cracks and inclusions, clouding of color and sensitivity to pressure. This is counteracted in the jewelry industry, for example, by stabilizing the stone with uncolored synthetic resins or by coloring it with colored oils and resins.

As one of the most valuable and correspondingly expensive gemstones, emerald is often supplemented or replaced by syntheses and imitations. Minerals that are similar in color, such as green-colored minerals from the tourmaline group , Dioptas and the garnet varieties Demantoid and Grossular are used as well as colored glass.

Others

The emerald or its green color is mentioned again and again in the literature. A novel by Kerstin Gier from the cycle Love Goes Through All Times, for example, was named Smaragdgrün . In 2016, the German film version of the same name was published.

The comic - superhero Green Lantern is also called due to its green costume emerald warrior or as Emerald Knights (in the English original Emerald Knight called).

See also

literature

  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Dörfler Verlag GmbH, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 220 .
  • Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 106-109 .
  • Bernhard Bruder: Beautified stones. Recognizing imitations and manipulations in gemstones and minerals . Neue Erde, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 97 .

Web links

Commons : Emerald  - collection of images, videos and audio files

Individual evidence

  1. ↑ Price evaluation of emeralds on greenfire-smaragde.de
  2. ↑ https://www.youtube.com/watch?v=hjMe94sQCRk
  3. ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 109 .
  4. ↑ spiegel.de: Suspicion of fraud against owner: Giant emerald remains at auction. spiegel.de, January 30, 2012, accessed August 26, 2015.
  5. ↑ Jewelery Stock Exchange
  6. ↑ a b Fochtmann emerald
  7. ↑ Largest emerald in the world exhibited in Bogotá. Krone.at , June 19, 2011, accessed on October 17, 2015.
  8. ↑ a b 1.1 kg and 5,655 carats: An emerald like no other has been unearthed in Zambia. CNN Style, October 30, 2018.
  9. ↑ TU Dresden / Institute for Geotechnics - Lecture Material - Mineral Raw Materials ( Memento from November 22, 2009 in the Internet Archive ) (p. 14)
  10. ↑ M. Lorenz: The occult meaning of precious stones. Devonshire Emerald, p. 41 in Google Book Search
  11. ↑ The World's Greatest Gemstones.Retrieved January 19, 2017
  12. ↑ Issue: DC Comics Collection 75 "Green Lantern - Wanted: Hal Jordan". www.comiccombo.de, 2016, accessed on October 27, 2016 .
  13. ↑ Green Lantern, Volume 1 (Panini). www.comicleser.de, May 25, 2016, accessed on October 27, 2016 .
  14. ↑ Green Lantern: Emerald Knights. Moviepilot , accessed October 27, 2016 .