Hessite

Hessite
	Hessite with small gold spots (size: 2.1 × 1.6 × 1.3 cm)
General and classification
other names	Tellurium silver; Tellurium silver luster; Botesite; Savodinskit; Hölzel no. 2.BA.600;
chemical formula	α-Ag 2 Te
Mineral class; (and possibly department)	Sulfides and sulfosalts
System no. to Strunz ; and to Dana	2.BA.30c ( 8th edition : II / B.05) ; 04/02/02/01
Crystallographic Data
Crystal system	monoclinic
Crystal class ; symbol	monoclinic prismatic; 2 / m
Space group	P 2 1 / c (No. 14)
Lattice parameters	a = 8.16 Å ; b = 4.47 Å; c = 8.98 Å ; β = 124.2 °
Formula units	Z = 4
Frequent crystal faces	{100}, {110}, {111}
Twinning	Twin slats visible in shiny sections
Physical Properties
Mohs hardness	2 to 3
Density (g / cm 3 )	measured: 8.24 to 8.45; calculated: 8.395
Cleavage	indistinct after {100}
Break ; Tenacity	even, smooth; can be cut with a knife
colour	lead gray to steel gray, tapering to black
Line color	light gray
transparency	opaque
shine	Metallic luster

Hessite , also known as tellurium silver , is a rarely occurring mineral from the mineral class of "sulfides and sulfosalts" with the chemical composition α-Ag ₂ Te and is therefore silver telluride from a chemical point of view .

Hessite crystallizes in the monoclinic crystal system and forms pseudocubic, irregularly grown crystals up to 1.7 centimeters in size, but also occurs in the form of compact masses or fine grains. The mineral is opaque in every form. The crystals are from lead to steel gray in color and have a metallic sheen on the surfaces . Over time, the surfaces can turn black.

Etymology and history

The mineral was first described by Gustav Rose in 1830 . He examined an ore that came from the Zavodinsky mine in the Altai region (Siberia) and was exhibited in the museum in Barnaul . There it had been mistaken for argentite . However, through investigations with the soldering tube and further tests, Rose quickly realized that it must be a silver-tellurium mineral, and accordingly referred to it as tellurium silver .

The mineral was given its name Hessit, which is still valid today, in 1843 from Julius Froebel , who named it after the Swiss-Russian chemist and mineralogist Germain Henri Hess (1802–1850).

Type material of the mineral is among other things in the mineral collection of the Museum für Naturkunde in Berlin (register no. 1999-7528 and 1999-0072).

classification

Already in the outdated, but still in use 8th edition of the mineral classification according to Strunz , the Hessite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides, selenides and tellurides with the molar ratio metal: S, Se, Te> 1: 1 ”, where together with aguilarite , acanthite , benleonardite , chenguodaite , cervelleite , empressite , naumannite , 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 was used by the International Mineralogical Association (IMA) until 2009, also assigns Hessite to the division of "B metal sulfides, M: S> 1: 1 (mainly 2: 1)" a. This is, however, 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 is the only member unnamed group forms 2.BA.30c .

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , assigns Hessite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here he can be found together with Cervelleit in the unnamed group 02.04.02 within the subsection “ Sulphides - including selenides and tellurides - with the composition A _m B _n X _p , with (m + n): p = 2: 1 ”.

Crystal structure

Hessite crystallizes in the monoclinic crystal system in the space group P 2 ₁ / c (space group no. 14) with the lattice parameters a = 8.164 Å , b = 4.468 Å, c = 8.977 Å and β = 124.16 ° as well as four formula units per unit cell . Template: room group / 14

Modifications and varieties

At a temperature of 155 ° C, hessite changes into a cubic form.

Education and Locations

Hessite forms under hydrothermal conditions at low or medium temperatures and in small quantities in pyrite deposits . The accompanying minerals include altaite , calaverite , chalcopyrite , empressite , galena , solid gold , petzite , pyrite , rickardite , sylvanite , tellurium and tetrahedrite .

As a frequent mineral formation, Hessite can be found in many localities, with around 760 localities so far (as of 2017) being known. In addition to the type locality, these include Sacarimb and Zlatna in Romania , Kalgoorlie in Australia , Fiji , Coquimbo in Chile , Canada and the US states of Colorado , California and Arizona .

use

Due to the high silver content of 63.3%, Hessite is a silver ore.

literature

Julius Froebel: 4th Guild: Monotrimetric Pyritoids. 1st family: Pyrrhotines. Hessite . In: Fundamentals of a system of crystallology or the natural history of inorganic individuals . Printing and publishing of the Literarisches Comptoir, Zurich and Winterthur 1843, p. 48–50 ( rruff.info [PDF; 319 kB ; accessed on July 25, 2017]).
Alfred J. Frueh, jr .: The structure of hessite, Ag ₂ Te-III . In: Journal of Crystallography . tape 112 , 1959, pp. 44–52 ( rruff.info [PDF; 2.9 MB ; accessed on July 25, 2017]).
Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 303 .

Web links

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

Mineral Atlas: Hessite
Mindat - Hessite (English)
RRUFF Database-of-Raman-spectroscopy - Hessite (English)
American-Mineralogist-Crystal-Structure-Database - Hessite (English)

Individual evidence

↑ ^a ^b Gustav Rose: About two tellurium ores from Altai. In: Poggendorff's annals of physics and chemistry. 1830, 18, pp. 64-71 ( digitized on Gallica ).
↑ ^a ^b ^c Uni Hamburg: Type material description Hessit
↑ ^a ^b ^c ^d 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. 66 .
^ ^A ^b Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 132 .
↑ ^a ^b ^c ^d Hessite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 64 kB ; accessed on July 25, 2017]).
↑ Mindat - Number of localities for Hessite (English)
↑ Find location list for Hessite in the Mineralienatlas and in Mindat

[Rose-1] Gustav Rose: About two tellurium ores from Altai. In: Poggendorff's annals of physics and chemistry. 1830, 18, pp. 64-71 ( digitized on Gallica ).

[TypkatalogHamburg-2] Uni Hamburg: Type material description Hessit

[StrunzNickel-3] 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. 66 .

[SchröckeWeiner-4] A ^b Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 132 .

[Datenblatt-5] Hessite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 64 kB ; accessed on July 25, 2017]).

[MindatAnzahl-6] Mindat - Number of localities for Hessite (English)

[Fundorte-7] Find location list for Hessite in the Mineralienatlas and in Mindat