Fettelite

(repeating unit)Ag16HgAs4S15 (rruff) or
[Ag6As2S7]·[Ag10HgAs2S8] (mindat.org)IMA symbolFtt[1]Strunz classification2.LA.30Crystal systemMonoclinicCrystal classSphenoidal (2)
(same H-M symbol)Space groupC2Unit cella = 15.00, c = 15.46 [Å]
V = 3014 Å3; Z = 8IdentificationColordark violet to redCrystal habitflakes, hexagonal, micaceousTwinningintimately twinned with six twin domainsCleavageperfectFracturesubconchoidalMohs scale hardness3.5LustermetallicStreakdark vermillionDiaphaneitysubopaque to opaqueSpecific gravity6.29Optical propertiesBiaxial, anisotrophism weak with strong red internal reflectionsRefractive indexN(calc) = 1.74Birefringencemoderate white to brownish grayReferences[2][3][4]

Fettelite, also known as sanguinite, is a mercury-sulfosalt mineral with the chemical formula Ag16HgAs4S15. The mineral was first described by Wang and Paniagua (1996)[5] who named it after M. Fettel, a German field geologist who collected the first samples from Odenwald.[6] It was first collected in the Nieder-Beerbach mine, 10 km south of Darmstadt, Odenwald, Germany. Its normal occurrence is in hydrothermal veins, which can cut gabbro-diorite intrusives. It is closely related to other rare minerals like dervillite, daomanite, vaughanite and criddleite which are also found in the same type locality as fettelite.[4]

Fettelite occurs as clusters of hexagonal flakes. These flakes can get up to 0.2 mm across and around 5-10 μm thick. In more complex hexagonal tablets, somewhat larger sub parallel aggregates can be measured.[7] The birefringence of Fettelite is moderate white to grayish brown.[6]

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineralienatlas
  3. ^ Mindat.org Accessed 4 November 2010
  4. ^ a b Jambor, John L.; Puziewicz, Jacek; Roberts, Andrew C. (1997). "New mineral name" (PDF). American Mineralogist. 82: 620–624.
  5. ^ Wang, N. and Paniagua, A. (1996) Fettelite, a new Hg-sulfosalt mineral from Odenwald. Neues Jahrbuch für Mineralogie Monatshefte, 82, 313–320.
  6. ^ a b Bindi, Luca; Keutsch, Frank N.; Francis, Carl A.; Menchetti, Silvio (2009). "Fettelite, {Ag6As2S7}{Ag10HgAs2S8} from Chañarcillo, Chile: Crystal structure, pseudosymmetry, twinning, and revised chemical formula" (PDF). American Mineralogist. 94: 609–615. doi:10.2138/am.2009.3096. S2CID 53975716.
  7. ^ Mandarino, J.A (1997) Abstracts of new mineral description The Mineralogical Record, 28, 141-143.


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