The tetrahedrite group: Nomenclature and classification

Abstract

The classification of the tetrahedrite group minerals in keeping with the current IMA-accepted nomenclature rules is discussed. Tetrahedrite isotypes are cubic, with space group symmetry I43m. The general structural formula of minerals belonging to this group can be written as M(2)A6M(1)(B4C2)X(3) D4S(1)Y12S(2)Z, where A = Cu+, Ag+, ☐ (vacancy), and (Ag6)4+ clusters; B = Cu+, and Ag+; C = Zn2+, Fe2+, Hg2+, Cd2+, Mn2+, Cu2+, Cu+, and Fe3+; D = Sb3+, As3+, Bi3+, and Te4+; Y = S2– and Se2–; and Z = S 2–, Se2–, and ☐. The occurrence of both Me+ and Me2+ cations at the M(1) site, in a 4:2 atomic ratio, is a case of valency-imposed double site-occupancy. Consequently, different combinations of B and C constituents should be regarded as separate mineral species. The tetrahedrite group is divided into five different series on the basis of the A, B, D, and Y constituents, i.e., the tetrahedrite, tennantite, freibergite, hakite, and giraudite series. The nature of the dominant C constituent (the so-called “charge-compensating constituent”) is made explicit using a hyphenated suffix between parentheses. Rozhdestvenskayaite, arsenofreibergite, and goldfieldite could be the names of three other series. Eleven minerals belonging to the tetrahedrite group are considered as valid species: argentotennantite-(Zn), argentotetrahedrite-(Fe), kenoargentotetrahedrite-(Fe), giraudite-(Zn), goldfieldite, hakite-(Hg), rozhdestvenskayaite-(Zn), tennantite-(Fe), tennantite-(Zn), tetrahedrite-(Fe), and tetrahedrite-(Zn). Furthermore, annivite is formally discredited. Minerals corresponding to different end-member compositions should be approved as new mineral species by the IMA-CNMNC following the submission of regular proposals. The nomenclature and classification system of the tetrahedrite group, approved by the IMA-CNMNC, allows the full description of the chemical variability of the tetrahedrite minerals and it is able to convey important chemical information not only to mineralogists but also to ore geologists and industry professionals.

Pošepnýite, a new Hg-rich member of the tetrahedrite group from Příbram, Czech Republic

“…Thus, the tetrahedral cation site was refined as Cu and Hg in mutual substitution, and with full resulting occupancy, the latter needed for the preservation of structural stability. The Sb site is fully occupied as well, and the small amount of Ag indicated by chemical analysis was ascribed to the copperoccupied triangular M2 sites, in agreement with the results of numerous studies of the tetrahedrite-tennantite group (e.g., Riley 1974;Sack and Loucks 1985;Lynch 1989;Biagioni et al 2020a). These assignments avoid any problems of Se1 anions without sufficient cation neighbors, which would lead to a structure collapse.…”

“…Vacancies are not very common in minerals of the tetrahedrite group but have been confirmed through structural studies (e.g., Maske and Skinner 1971;Makovicky and Skinner 1979;Rozhdestvenskaya et al 1993;Makovicky et al 2005;Welch et al 2018). The chemical vari ability encompasses anions too, with the substitution of S by Se, or with the occurrence of vacancies (Biagioni et al 2020a).…”

“…x restricted to the range 0 ≤ x << 2; results of the The general structural formula of the tetrahedrite group minerals can be best defined as Biagioni et al 2020a). Pošepnýite is the first member of the tetrahedrite group with the content of divalent metal (Hg) significantly higher than 2 apfu.…”

Tetrahedrite-(Hg), a new ‘old’ member of the tetrahedrite group

“…rozhdestvenskayaite and goldfieldite) belong to this group. Biagioni et al (2020), on the basis of literature data, defined thirty-two potential endmember compositions within the tetrahedrite group; among them eleven can be considered as valid species, whereas the remaining phases have to be approved officially by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA-CNMNC).…”

Terrywallaceite from the Kochkar Au Deposit, South Urals: First Find in Russia

“…для блеклой руды характерно резкое преобладание Cu над Ag, Sb над As и Fe над Zn. согласно недавно принятой номенклатуре блеклых руд, такой состав отвечает тетраэдриту-(Fe) (Biagioni et al, 2020). висмутин существенно обогащен Sb (до 22 мас.…”