Naumannite

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Naumannite
General and classification
other names
  • Selenium lead silver
  • Selenium silver
  • Selenium silver sheen
chemical formula Ag 2 Se
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.BA.30b ( 8th edition : II / B.05)
04/02/01/02
Similar minerals Acanthite, aguilarite, argentite, benleonardite, cervelleite, empressite, hessite, kurilite, stiitzite, tsnigriite
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-disphenoidic; 222
Space group P 2 1 2 1 2 1 (No. 19)Template: room group / 19
Lattice parameters a  = 4.333  Å ; b  = 7.062 Å; c  = 7.764 Å
Formula units Z  = 4
Twinning mimetic twin structure very clear in places
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) 7.0 to 8.0 (measured); 8.24 (calculated)
Cleavage is missing
Break ; Tenacity hooked; can be cut and hammered
colour gray to iron black, tapering to brown
Line color black
transparency opaque (opaque)
shine lighter, but strongly darkening metal sheen
Other properties
Chemical behavior Very difficult to dissolve in dilute nitric acid, easily soluble in fuming nitric acid; strong precipitate of AgCl with hydrochloric acid
Special features Semiconductor, the high temperature form, is a good electrical conductor and a super ionic conductor

Naumannite , outdated also known as selenium silver , selenium lead silver or selenium silver luster , is a relatively rare mineral from the mineral class of " sulfides and sulfosalts " with the chemical formula Ag 2 Se. Chemically speaking, naumannite is therefore a silver (I) selenide that is structurally related to sulphides.

Naumannite crystallizes in the orthorhombic crystal system and develops predominantly granular to massive aggregates , but also idiomorphic, pseudocubic, maximally 1 cm large crystals of gray to iron-black color, which typically turn brownish.

Etymology and history

Namesake Karl Friedrich Naumann

The Berlin mineralogist Gustav Rose , who found the mineral in 1828 "under the steps of selenium lead from Tilkerode in the eastern Harz, which are in the Royal Mineral Collection in Berlin", is considered to be the discoverer of naumannite . It was not until 1845 that the Viennese mineralogist Wilhelm von Haidinger introduced the name naumannite in honor of the Saxon geologist and crystallographer Carl Friedrich Naumann .

The mineral must not be confused with the “naumannite” described by Nikolai Iwanowitsch Kokscharow in 1854 , which has proven to be rutile (Ilmenorutil) containing niobium .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the naumannite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides, selenides and tellurides with a ratio of metal: S, Se, Te> 1: 1 ", Where together with aguilarite , acanthite (> 177 ° C: argentite ), benleonardite , chenguodaite ( IMA2004-042a ), cervelleite , empressite , hessite , supportite and tsnigriite the" argentite-naumannite group "with the system no. II / B.05 .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns naumannite to the class of “sulfides and sulfosalts”, but there in the department of “metal sulfides, M: S> 1 : 1 (mainly 2: 1) ”. This is further subdivided according to the predominant metals in the compound, so that the mineral can be found according to its composition in the sub-section "with copper (Cu), silver (Ag), gold (Au)", where it can only be found together with Aguilarit forms the unnamed group 2.BA.30b .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns naumannite to the class of "sulphides and sulphosalts" and there in the category of "sulphide minerals". Here it is together with acanthite and aguilarite in the "acanthite group" with system no. 04/02/01 within the subsection “ Sulphides - including selenides and tellurides - with the composition Am Bn Xp, with (m + n): p = 2: 1 ”.

Crystal structure

Crystallographic Data
Ag2Sestructure.png

Crystal structure of naumannite
Crystal system orthorhombic
Space group P 2 1 2 1 2 1 (No. 19)Template: room group / 19
Lattice parameter
(unit cell ) 		a  = 4.333  Å ; b  = 7.062 Å;

c  = 7.764 Å

Number (Z) of the
formula units 		Z = 4

Naumannite crystallizes in the orthorhombic crystal system in the space group P 2 1 2 1 2 1 (space group no. 19) with the lattice parameters a  = 4.333  Å ; b  = 7.062 Å; c  = 7.764 Å and four formula units per unit cell . It has been known since 1936 that naumannite changes into a cubic-hexakisoctahedral high-temperature form at a temperature of 127–143 ° C, which is referred to as α-Ag 2 Se . The space group of this high-temperature form is Im 3 m (space group no. 229) and the lattice parameter is a  = 5.006 Å with 2 formula units per unit cell . Template: room group / 19

The structure of naumannite is composed of Se layers and two crystallographically independent Ag atoms. One Ag atom is in the immediate vicinity of the Se layer and is surrounded by four Se atoms in a disturbed tetrahedral coordination, while the second Ag atom lies between the Se layers and has a [3 + 1] coordination. This is defined by three closely spaced Se atoms forming a trigonal surface and one Se atom located at a distance.

properties

morphology

Naumannite mainly develops granular to massive, but also thin-plate and even dendritic aggregates . Idiomorphic, pseudocubic crystals , maximum 1 cm in size, are much rarer . From the Tilkerode type locality in addition to platy aggregates up to centimeters in size, especially as a teardrop-shaped inclusion in Clausthalite as well as in larger independent, sometimes beautifully lamellar twinned masses. In the De Lamar Mine in Idaho's Silver City District, naumannite occurred in the form of xenomorphic, bulbous aggregates; From the unusually rich “Silver Stopes” a piece weighing 475 g was described. Furthermore, in addition to indistinct also in idiomorphic crystals. Cubic crystals formed at temperatures> 133 ° C were found on dikes and in drusen, well-formed platy crystals were also found in drusen, which suggest crystallization at temperatures <133 ° C. Large naumannite crystals come from the Midas Mine in the Gold Circle District, Nevada, for which, however, multiple banded ores rich in naumannite and electrum with a collomorphic texture in quartz and adulara are typical. Naumannite from the Bolivian deposit Virgen de Surumi develops very shiny crystals with flowing surfaces that sit on crystallized siderite .

Naumannite can be artificially produced by the action of selenium vapors permeated with a slow stream of nitrogen on silver in red heat . The thin needles that are up to 2 cm long are initially formed and are transformed into steel-gray rhombic dodecahedra upon further exposure .

physical and chemical properties

The crystals and aggregates of naumannite are gray to iron black in color and typically turn brown. Your stroke color is black. They have a light, but strongly darkening metallic sheen. The complete cleavage according to {001} observed since the first description of naumannite is actually a divisibility that results from the phase transition from the high-temperature modification to the actual naumannite. With a Mohs hardness of 2.5, naumannite is one of the soft to medium-hard minerals that are slightly easier to scratch with a copper coin than the reference mineral calcite .

In reflected light (bevel), naumannite is bluish-gray and shows (in air) a moderately high reflection behavior, somewhat lighter than tiemannite . The reflection behavior is greatly reduced in oil; the color changes slightly to brown. The reflection pleochroism is difficult to see in air, weak but clear in oil, between brownish-gray and pale greenish gray-brown (darker). The anisotropy effects at + N are high, the color effects (from pale gray to dark gray) are quite vivid. Naumannite can be easily melted on carbon in front of the soldering tube and gives a grain of silver with soda. Can also be melted in the flask in front of the soldering tube with the formation of a slight sublimate ; In the open tube, small, star-shaped crystals form over a sublimate of red selenium, and the air rising from the tube smells strongly of selenium . Very difficult to dissolve in dilute nitric acid, easily soluble in fuming nitric acid; strong precipitation of silver chloride with hydrochloric acid .

Modifications and varieties

The variety selenium silver lead consists of a mixture of Clausthalite and Naumannite. Cacheutaït , named after the Cerro de Cacheuta near Mendoza in Argentina, describes a mixture of different selenides, mainly Clausthalite.

Education and Locations

Naumannite forms hydrothermally and is found mainly on low-thickness, sulfur- deficient hydrothermal selenium veins. Begleitminerale are other selenides as Aguilarit , Bohdanowiczit , Clausthalit , Eskebornite , Eukairit , Tiemannite and Umangite , sulfides and sulfosalts as bornite , chalcopyrite , Digenite , Mawsonit , Akanthit , Ag-rich tetrahedrite , Proustite and Pyrargyrite and the Ag-Au alloy electrum , Goethite , carbonates and various silicates. Very delicate myrmekitic adhesions occur with Clausthalit. Locally, secondary minerals containing silver or selenium such as chlorine argyrite , chalcomenite , but also malachite , are characteristic.

As a rather rare mineral formation, naumannite can sometimes be abundant at various sites, but overall it is not very common. So far (as of 2016) around 170 sites are known. The type locality for the naumannite is the Eskaborner tunnel near Tilkerode , Saxony-Anhalt ; the mineral was also observed in the nearby Grauwackesteinbruch Rieder near Gernrode . Other sites in Germany include the “Red Bear” pit, St. Andreasberg , the “St. Lorenz ”and“ Charlotte ”, Burgstätter Gangzug, Clausthal-Zellerfeld , and the“ Brummerjahn ”mine near Zorge (all in the Harz , Lower Saxony ). Also from the Clara mine in the Rankach Valley near Oberwolfach , Black Forest , Baden-Württemberg , as well as from the corridors “Tiber”, “Brahma”, “Brahmaputra”, “Nelson”, “Rio Tinto”, “Rio Madeira”, “Glorious” "," Babelsberg "," Oslo "," Hohenstein "," Sinaida "and" Dürre Henne "in the reserve area of Niederschlema-Alberoda ( Saxony ).

In Austria , naumannite is only known from a small quarry near the Judenbauer, northwest of Kirchschlag in the Bucklige Welt , Lower Austria . From Switzerland are with Weierfeld , Rheinfelden , Aargau , and Van d'en Bas, Trent Valley , canton of Valais two localities are known. In Weierfeld, the mineral occurs in rock samples from a Red Bed deposit from the Permian . From selenium mineralization in uraninite-calcite veins from Předbořice ( Kovářov ), from Zálesí , Olomouc Region , Moravia and from Moldava near Teplice , Ore Mountains , Aussiger Region (all in the Czech Republic ). From the “Rozalia” corridor, Hodruša-Hámre near Banská Štiavnica , Slovakia , and from Săcărîmb (Nagyág) near Deva , Romania . From the pits “St. Johannes ”and“ Hellig Trefoldighet ”of the Kongsberg silver ore deposit , Kongsberg , Buskerud , Norway . From the “Skrikerum Mine”, Valdemarsvik , Östergötland , and the Glava copper field (Yttre Rud Mines), Arvika , Värmland , both Sweden . Also from Hope's Nose , Torquay , Devon (England) .

In the USA from the "Republic District", Ferry County , and the "LD Mine", Wenatchee , Chelan County , both Washington ; from the De Lamar Mine, Silver City District, Owyhee County , and from the 4th of July Mine, Yankee Fork, Custer County , Idaho ; from the "Midas Mine" (Ken Snyder Mine) and the Rex Grande deposit near Midas , both in the Gold Circle District in Elko County , Nevada . From Canada from the Betty Claims north of Divide Lake, British Columbia , and the world's deepest non-ferrous metal mine, the Kidd Creek Mine near Timmins , Ontario . In Mexico from the El Capulin, El Cubo San Juan de Rayas and Flores de María mines, all near Guanajuato , Municipio Guanajuato, Guanajuato . From the famous Virgen de Surumi silver deposit (Pacajake Mine) near Colquechaca , Potosí , Bolivia . From the Mina Tumiñico, Sierra de Cacho , La Rioja province , and from what was once the most selenium-rich ore in the world at Cerro de Cacheuta near Mendoza , both Argentina .

In Australia from the Wolumia Goldfield, New South Wales , and the Copper Hills, Eastern Pilbara Region , Western Australia . From the Emperor Mine, Vatukoula, and the Au-Ag-Te gold field Tuvatu, Viti Levu , Fiji . In Japan, from the Hishikari and Kushikino Au-Ag deposits, Kagoshima Prefecture , and the Sanru mine in Hokkaido . From the Axi gold deposit, Ili, Xinjiang Uyghur Autonomous Region , China .

Further points of discovery are z. B. in Argentina , Australia , Bulgaria , China , Finland , Germany , France , Greenland , Indonesia , Japan , Canada , Mexico , Poland , Russia , Spain , Czech Republic , Uzbekistan and several states in the USA .

use

Naumannite consists of about 73% silver and about 27% selenium and is therefore a rich silver ore. Naumannite from the “De Lamar Mine” in the Silver City District, Idaho, was mined and smelted as “argentite” for decades and only recognized as silver selenide in 1920. Naumannite is practically the only silver ore in the Midas Mine in Nevada's Gold Circle District. Naumannite is one of the selenium ores that were selectively mined and smelted from 1961–1965 in the Niederschlema-Alberoda deposit area in Saxony .

Ag 2 Se is a promising material for technological applications in various fields such as thermochromic materials for nonlinear optical devices, ion-sensitive multiple electrodes, infrared sensors, electrochemical storage cells, storage devices for electrochemical potentials and magnetic field sensors. The low-temperature modification is an N-type semiconductor and is used as a thermochromic material and as a photosensitizer in photographic films, while the high-temperature modification is a super ion conductor and is used as a solid electrolyte in light-active rechargeable batteries. After the phase transition, the ionic conductivity increases with values ​​around 2 S / cm to ten thousand times. The semiconductor properties of the material are size-dependent - semiconductor nanocrystals are used in solar cells, light-emitting diodes, thin-film transistors and in biological image processing.

See also

literature

  • Naumannite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 58 kB )

Web links

Individual evidence

  1. ^ A b Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  77 .
  2. ↑ a b c Gustav Rose : About a new selenium from the Harz . In: Annals of Physics and Chemistry . tape  90 . Verlag Johann Ambrosius Barth , Leipzig 1828, p. 471–473 ( available online in Poggendorff's Annalen der Physik und Chemie p. 471 ff. In the Google book search).
  3. ^ A b Bernhard Pracejus: The ore minerals under the microscope, An optical guide . 2nd Edition. Elsevier, Amsterdam 2015, ISBN 978-0-444-62725-4 , pp. 216 f .
  4. ↑ a b c d Paul Ramdohr : The ore minerals and their adhesions . 4th edition. Akademie-Verlag, Berlin 1975, p.  513-515 .
  5. ↑ a b c d e f g Naumannite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 57, 8 kB )
  6. ↑ a b c d e Carl Hintze : Handbook of Mineralogy. First volume. First division . 1st edition. Verlag Veit & Co., Leipzig 1904, p. 455.
  7. ↑ a b c d UM Chougale, SH Han, MC Rath, VJ Fulari (2013): Synthesis, characterization and surface deformation study of nanocrystalline Ag 2 Se thin films. In: Materials Physics and Mechanics , Volume 17, 47-58.
  8. ↑ Mindat - Naumannite
  9. ^ Wilhelm von Haidinger : Handbook of determining mineralogy: containing the terminology, systematics, nomenclature and characteristics of the natural history of the mineral kingdom . 2nd Edition. Braumüller & Seidel, Vienna 1845, p.  565 ( available online in the Handbook of Determining Mineralogy p. 565 in the Google book search).
  10. ↑ Mindat - Naumannit von Kokscharow
  11. ↑ M. Oliviera, RK McMullan, BJ Wuensch (1988): Single crystal neutron diffraction analysis of the cation distribution in the high-temperature phases α-Cu 2-x S, α-Cu 2-x Se, and α-Ag 2 Se . In: Solid State Ionics , Vol. 28-30, 1332-1337.
  12. ↑ Jaemin Yu, Hoseop Yun: Reinvestigation of the low-temperature form of Ag 2 Se (naumannite) based on single-crystal data . In: Acta Crystallogr. Sect. E Struct. Rep. Online . 2011, 67 (Pt 9), i45. doi: 10.1107 / S1600536811028534 .
  13. ↑ Gerhard Tischendorf : On the genesis of some selenide occurrences, in particular from Tilkerode in the Harz (Freiberg research booklet C69) . 1st edition. Akademie-Verlag, Berlin 1959, p.  62-63 .
  14. ^ A b Earl V. Shannon (1920): An Occurrence of Naumannite in Idaho , In: American Journal Science , Volume 50, 390-391.
  15. ^ A b Robert E. Thomason (1983): Volcanic stratigraphy and epithermal mineralization of the DeLamar Silver Mine, Owyhee County, Idaho. Unpubl. M. Sc. Thesis, Oregon State University, 111 pp.
  16. ↑ Hans Block, Friedrich Ahlfeld (1937): The Selenium ore deposit Pacajake, Bolivia , In: Journal of practical geology , Volume 45, 9-14.
  17. ↑ JW Earley (1950): Description and synthesis of the selenide minerals , In: American Mineralogist , Volume 35, pp. 337-364 ( PDF, 1850 kB ).
  18. ↑ Mindat - Number of localities for naumannite
  19. ↑ a b Axel Hiller, Werner Schuppan (2008): Geology and Uranium Mining in the Schlema-Alberoda Revier , In: Bergbau in Sachsen , Mining Monograph Volume 14, 171 pp. (Ed .: Saxon State Office for Environment, Agriculture and Geology, Dresden).
  20. ^ Alfred Stelzner : Mineralogical observations in the area of ​​the Argentine Republic . In: Tschermaks Mineralogische Mittheilungen . tape  1873 . Verlag Wilhelm Braumüller, Vienna 1873, p. 219-254 ( available online in Tschermaks Mineralogische Mittheilungen pp. 219-254 in the Google book search).
  21. ↑ Find location list for naumannite in the Mineralienatlas and Mindat
  22. ↑ F. Kirchhoff, JM Holender, MJ Gillan (1996): Structure, dynamics, and electronic structure of liquid Ag-Se alloys investigated by ab initio simulation . In: Physical Review , Volume B54, p. 190. doi: 10.1103 / PhysRevB.54.190 .