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Hessite

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Germain Henri Hess
Formula:
Ag2Te
System:
Monoclinic
Colour:
lead-grey, steel-grey
Hardness:
2 - 3
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

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
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
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Type Occurrence of Hessite

Year of Discovery:
1843

Occurrences of Hessite

Geological Setting:
Low to medium temperature hydrothermal deposits.

Physical Properties of Hessite

Metallic
Diaphaneity (Transparency):
Opaque
Colour:
lead-grey, steel-grey
Comment:
Tarnishing to black
Streak:
black
Hardness (Mohs):
2 - 3
Hardness (Vickers):
VHN100=22 - 24 kg/mm2
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)

Crystallography of Hessite

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

Optical Data of Hessite

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

Chemical Properties of Hessite

Formula:
Ag2Te
Essential elements:
All elements listed in formula:
Common Impurities:
Au,Pb

Relationship of Hessite to other Species

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)
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

Other Names for Hessite

Name in Other Languages:

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:
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

Specimens:
The following Hessite specimens are currently listed for sale on minfind.com.

Localities for Hessite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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