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Hessite

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Germain Henri Hess
Formula:
Ag2Te
Colour:
lead-grey, steel-grey
Lustre:
Metallic
Hardness:
2 - 3
Specific Gravity:
8.24 - 8.45
Crystal System:
Monoclinic
Name:
Named in 1843 by Frobel in honor of Germain Henri Hess [August 7, 1802 Geneva, Switzerland - November 30, 1850 St. Petersburg, Russia], Swiss-Russian chemist who proposed Hess's Law, which stated that the final thermodynamic energy of a series of chemical reactions is independent of the chemical pathway to that state. Earlier called tellursilber by Rose and later confounded with petzite and other species. Hess was a student of Jons Jakob Berzelius.
Above 155°C hessite is cubic, and on cooling below this temperature it develops fine phase transformation lamellae.


Classification of Hessite

Approved, 'Grandfathered' (first described prior to 1959)
2.BA.60

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
B : Metal Sulfides, M: S > 1: 1 (mainly 2: 1)
A : With Cu, Ag, Au
2.4.2.1

2 : SULFIDES
4 : AmBnXp, with (m+n):p = 2:1
3.2.5

3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
2 : Sulphides etc. of Ag

Physical Properties of Hessite

Metallic
Transparency:
Opaque
Colour:
lead-grey, steel-grey
Comment:
Tarnishing to black
Streak:
black
Hardness:
2 - 3 on Mohs scale
Hardness:
VHN100=22 - 24 kg/mm2 - Vickers
Tenacity:
Sectile
Cleavage:
Poor/Indistinct
indistinct on {100}
Comment:
Even to smooth fracture
Density:
8.24 - 8.45 g/cm3 (Measured)    8.4 g/cm3 (Calculated)

Optical Data of Hessite

Type:
Anisotropic
Anisotropism:
Distinct from dark orange to dark blue

Chemical Properties of Hessite

Formula:
Ag2Te
Common Impurities:
Au,Pb

Crystallography of Hessite

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/c
Cell Parameters:
a = 8.13 Å, b = 4.48 Å, c = 8.09 Å
β = 112.9°
Ratio:
a:b:c = 1.815 : 1 : 1.806
Unit Cell V:
271.43 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Pseudocubic, highly modified, massive
Twinning:
twin lamellae visible in polished section

Type Occurrence of Hessite

Synonyms of Hessite

Other Language Names for Hessite

Common Associates

Associated Minerals Based on Photo Data:
Gold81 photos of Hessite associated with Gold on mindat.org.
Quartz80 photos of Hessite associated with Quartz on mindat.org.
Coloradoite42 photos of Hessite associated with Coloradoite on mindat.org.
Sylvanite39 photos of Hessite associated with Sylvanite on mindat.org.
Chalcopyrite15 photos of Hessite associated with Chalcopyrite on mindat.org.
Petzite12 photos of Hessite associated with Petzite on mindat.org.
Galena9 photos of Hessite associated with Galena on mindat.org.
Calaverite8 photos of Hessite associated with Calaverite on mindat.org.
Benleonardite6 photos of Hessite associated with Benleonardite on mindat.org.
Kutnohorite6 photos of Hessite associated with Kutnohorite on mindat.org.

Related Minerals - Nickel-Strunz Grouping

2.BA.05ChalcociteCu2S
2.BA.05DjurleiteCu31S16
2.BA.05GeeriteCu8S5
2.BA.05RoxbyiteCu9S5
2.BA.10AniliteCu7S4
2.BA.10DigeniteCu9S5
2.BA.15BorniteCu5FeS4
2.BA.20BellidoiteCu2Se
2.BA.20BerzelianiteCu2Se
2.BA.25AthabascaiteCu5Se4
2.BA.25UmangiteCu3Se2
2.BA.30RickarditeCu7Te5
2.BA.30WeissiteCu2-xTe
2.BA.35AcanthiteAg2S
2.BA.40MckinstryiteAg5-xCu3+xS4
2.BA.40StromeyeriteAgCuS
2.BA.40dUM2003-13-S:AgAuCuAg6AuCu2S5
2.BA.45JalpaiteAg3CuS2
2.BA.45SelenojalpaiteAg3CuSe2
2.BA.50EucairiteAgCuSe
2.BA.55AguilariteAg4SeS
2.BA.55NaumanniteAg2Se
2.BA.60CervelleiteAg4TeS
2.BA.60ChenguodaiteAg9Fe3+Te2S4
2.BA.65Henryite(Cu,Ag)3+xTe2 , with x ~ 0.40
2.BA.65StütziteAg5-xTe3, x = 0.24-0.36
2.BA.70ArgyroditeAg8GeS6
2.BA.70CanfielditeAg8SnS6
2.BA.70Putzite(Cu4.7Ag3.3)GeS6
2.BA.75FischesseriteAg3AuSe2
2.BA.75Penzhinite(Ag,Cu)4Au(S,Se)4
2.BA.75PetrovskaiteAuAg(S,Se)
2.BA.75PetziteAg3AuTe2
2.BA.75UytenbogaardtiteAg3AuS2
2.BA.80Bezsmertnovite(Au,Ag)4Cu(Te,Pb)
2.BA.80BilibinskitePbCu2Au3Te2
2.BA.80Bogdanovite(Au,Te,Pb)3(Cu,Fe)

Related Minerals - Hey's Chemical Index of Minerals Grouping

3.2.1AcanthiteAg2S
3.2.3NaumanniteAg2Se
3.2.4AguilariteAg4SeS
3.2.6EmpressiteAgTe
3.2.7StütziteAg5-xTe3, x = 0.24-0.36
3.2.8CervelleiteAg4TeS
3.2.9DervilliteAg2AsS2
3.2.10StromeyeriteAgCuS
3.2.11MckinstryiteAg5-xCu3+xS4
3.2.12JalpaiteAg3CuS2
3.2.13EucairiteAgCuSe
3.2.14CameroniteCu5-x(Cu,Ag)3+xTe10 (x = 0.43)
3.2.15Henryite(Cu,Ag)3+xTe2 , with x ~ 0.40
3.2.16SternbergiteAgFe2S3
3.2.17ArgentopyriteAgFe2S3
3.2.18Geffroyite(Cu,Fe,Ag)9(Se,S)8
3.2.19ArgentopentlanditeAg(Fe,Ni)8S8

Related Minerals - Dana Grouping (8th Ed.)

2.4.2.2IMA2009-080Ag8Te3Se

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
Silver ore

References for Hessite

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Hillebrand, William Francis (1899) Mineralogical notes: melonite (?), coloradoite, petzite, hessite: American Journal of Science, 4th. series: 8: 295-298.
Borchert (1930) [on phase transition at 155°C].
Palache, Charles, Harry Berman & Clifford Frondel (1944) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged, 834pp.: 184-186.
Thompson, R.M. (1949) The telluride minerals and their occurrence in Canada. American Mineralogist: 34: 342-382.
Van der Lee, A. and J.L. de Boer (1959) Redetermination of the structure of hessite, Ag2Te-III. Acta Crystallographica: C49: 1444-1446.
Criddle, A.J. and C.J. Stanley, Eds., (1993) Quantitative data file for ore minerals, 3rd. edition. Chapman & Hall, London: 237.
Zeitschrift für Kristallographie: 112: 44-52.

Internet Links for Hessite

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https://www.mindat.org/min-1881.html
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Specimens:
The following Hessite specimens are currently listed for sale on minfind.com.

Localities for Hessite

Mineral and/or Locality  
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