Hessite
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Germain Henri Hess
Formula:
Ag2Te
System:
Monoclinic
Colour:
lead-grey, steel-grey
Lustre:
Metallic
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
Approved, 'Grandfathered' (first described prior to 1959)
2/B.05-40
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 : 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
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
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
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}
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
Elements listed in formula:
Common Impurities:
Au,Pb
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°
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
Occurrences of Hessite
Type Occurrence of Hessite
Relationship of Hessite to other Species
| 2.BA.05 | Chalcocite | Cu2S |
| 2.BA.05 | Djurleite | Cu31S16 |
| 2.BA.05 | Geerite | Cu8S5 |
| 2.BA.05 | Roxbyite | Cu1.78S |
| 2.BA.10 | Anilite | Cu7S4 |
| 2.BA.10 | Digenite | Cu1.8S |
| 2.BA.15 | Bornite | Cu5FeS4 |
| 2.BA.20 | Bellidoite | Cu2Se |
| 2.BA.20 | Berzelianite | Cu2-xSe (x~0.12) |
| 2.BA.25 | Athabascaite | Cu5Se4 |
| 2.BA.25 | Umangite | Cu3Se2 |
| 2.BA.30 | Rickardite | Cu3-xTe2 |
| 2.BA.30 | Weissite | Cu5Te3 |
| 2.BA.35 | Acanthite | Ag2S |
| 2.BA.40 | Mckinstryite | Ag5Cu3S4 |
| 2.BA.40 | Stromeyerite | CuAgS |
| 2.BA.40d | UM2003-13-S:AgAuCu | Ag6AuCu2S5 |
| 2.BA.45 | Jalpaite | Ag3CuS2 |
| 2.BA.45 | Selenojalpaite | Ag3CuSe2 |
| 2.BA.50 | Eucairite | CuAgSe |
| 2.BA.55 | Aguilarite | Ag4SeS |
| 2.BA.55 | Naumannite | Ag2Se |
| 2.BA.60 | Cervelleite | Ag4TeS |
| 2.BA.60 | Chenguodaite | Ag9FeTe2S4 |
| 2.BA.65 | Henryite | Cu4Ag3Te4 |
| 2.BA.65 | Stützite | Ag5-xTe3 (x = 0.24-0.36) |
| 2.BA.70 | Argyrodite | Ag8GeS6 |
| 2.BA.70 | Canfieldite | Ag8SnS6 |
| 2.BA.70 | Putzite | (Cu,Ag)8GeS6 |
| 2.BA.75 | Fischesserite | Ag3AuSe2 |
| 2.BA.75 | Penzhinite | (Ag,Cu)4Au(S,Se)4 |
| 2.BA.75 | Petrovskaite | AuAgS |
| 2.BA.75 | Petzite | Ag3AuTe2 |
| 2.BA.75 | Uytenbogaardtite | Ag3AuS2 |
| 2.BA.80 | Bezsmertnovite | (Au,Ag)4Cu(Te,Pb) |
| 2.BA.80 | Bilibinskite | Au3Cu2Pb · nTeO2 |
| 2.BA.80 | Bogdanovite | (Au,Te,Pb)3(Cu,Fe) |
| 3.2.1 | Acanthite | Ag2S |
| 3.2.3 | Naumannite | Ag2Se |
| 3.2.4 | Aguilarite | Ag4SeS |
| 3.2.6 | Empressite | AgTe |
| 3.2.7 | Stützite | Ag5-xTe3 (x = 0.24-0.36) |
| 3.2.8 | Cervelleite | Ag4TeS |
| 3.2.9 | Dervillite | Ag2AsS2 |
| 3.2.10 | Stromeyerite | CuAgS |
| 3.2.11 | Mckinstryite | Ag5Cu3S4 |
| 3.2.12 | Jalpaite | Ag3CuS2 |
| 3.2.13 | Eucairite | CuAgSe |
| 3.2.14 | Cameronite | Cu5-x(Cu,Ag)3+xTe10 (x = 0.43) |
| 3.2.15 | Henryite | Cu4Ag3Te4 |
| 3.2.16 | Sternbergite | AgFe2S3 |
| 3.2.17 | Argentopyrite | AgFe2S3 |
| 3.2.18 | Geffroyite | (Cu,Fe,Ag)9Se8 |
| 3.2.19 | Argentopentlandite | Ag(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.
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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http://www.mindat.org/min-1881.html
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Botești, Zlatna, Alba Co., Romania