La hocartite, Ag2SnFeS4, une nouvelle espèce minérale

Abstract

Un nouveau sulfure d'argent, étain et fer a été découvert dans le minerai de Tacama (Bolivie). Sa composition chimique, obtenue à la microsonde électronique (4 analyses) correspond étroitement à la formule Ag₂SnFeS₄ et en fait l'équivalent argentifère de la stannite. Son diagramme de poudre, voisin de celui de la stannite a pu être indicé dans le système quadratique avec comme paramètres a = 5,74 et c = 10,96. Sa couleur en section polie est gris brunâtre légèrement différente de celle de la stannite et très proche de celle de la canfieldite. Les courbes de dispersion des pouvoirs réflecteurs ont été établies ; elles montrent que le minéral est uniaxe négatif. Le nom de hocartite est proposé en l'honneur du professeur R. Hocart.

Crystal structure of mechanochemically synthesized Ag2CdSnS4

“…For Ag 2 CdSnS 4 , space group Cmc2 1 is mentioned in the literature with Ag, Cd, and Sn distributed statistically on the position 4a with (0, 0.167, 0.370) and S on another 4a position with (0, 0.176, 0.997) [20]. Similar compounds containing silver either crystallize in cubic diamond/sphalerite-related structures such as the stannite-or kesterite-type structure (such as Ag 2 Zn-SnS 4 [14], Ag 2 FeSnS 4 [13], Ag 2 ZnGeS 4 [24]) or in crystal structures derived from the hexagonal diamond/wurtzite type providing non-equivalent positions for the cations/anions (the wurtzstannite-type structure (space group Pmn2 1 ) and its derivatives with space group Pn (wurtzkesteritetype structure) or Pna2 1 ). Compounds crystallizing in the wurtzstannite-type structure are Ag 2 CdGeS 4 [4] and Ag 2 HgSnS 4 [15], whereas Ag 2 MnSnS 4 [18] and Si-bearing compounds such as Ag 2 FeSiS 4 [16] and Ag 2 ZnSiS 4 [17] crystallize in the wurtzkesterite-type structure.…”

“…Ag-containing compounds are more difficult to synthesize and less stable. Nevertheless, a few A 2 I B II C IV X 4 phases with A = Ag are known so far [4,[13][14][15][16][17][18][19]. For most Ag compounds, a stannite-or wurtzstannite-/wurtzkesterite-type structure has been presented in the literature.…”

Stannites – A New Promising Class of Durable Electrocatalysts for Efficient Water Oxidation

“…Quaternary sulfides or selenides of the formula usually contain three different metals. A great variety of (semi)metals can be implemented for example A =Li, Na, Ag, Cu; B =Mn, Fe, Co, Ni, Zn, Cd; and C =Si, Ge, Sn . Many members of this class of materials crystallize in the stannite structure type named after the mineral stannite with the formula Cu 2 FeSnS 4 .…”

Synthesis, structural characterization and differential thermal analysis of the quaternary compound Ag2MnSnS4

“…However, it has been more recently reported, with no structural details [38], that Furthermore, Ag 2 MnSnS 4 is one of the three sulfide minerals containing silver and tin found in nature. They are the hocartite, Ag 2 FeSnS 4 , found in Bolivia in 1967 [39], the pirquitasite, Ag 2 ZnSnS 4 , found in Argentina in 1980 [40], and the agmantinite, Ag 2 MnSnS 4 , found in Perú in 2014 [41], whose name has been recently approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association [41].…”