Work

Boevskite, Pb 4 (TeO 3 ) 2 (SO 4 )(S 2 O 3 ), the first mixed sulfate–thiosulfate mineral from the Boevskoe deposit, Southern Urals, Russia

Year: 2025

Type: article

Abstract: The new mineral boevskite Pb 4 (TeO 3 ) 2 (SO 4 )(S 2 O 3 ) was found at the Boevskoe W-Be deposit, Chelyabinsk Oblast, Southern Urals, Russia. It occurs as very rare euhedral grains up to 0.25 mm at the contact of galena and pyrite, as inclusions in galena up to 0.2 mm, and as thin veinlets up to 0.2 × 0.03 mm filling cracks in sphalerite. Other associated minerals include anglesite, cerussite, chalcopyrite, empressite, hessite, ingodite, joséite-B, matildite and pyrrhotite. Boevskite is colourless and transparent with an adamantine lustre. It is brittle, with uneven fracture. No cleavage or parting are observed. The Vickers’ micro-indentation hardness (VHN, 10 g load) is 110 kg/mm 2 , corresponding to a Mohs’ hardness of 2.5–3. D calc. = 6.599 g/cm 3 . Boevskite is optically biaxial, colourless and nonpleochroic. The mean refractive index calculated using the Gladstone–Dale equation is 2.08. The empirical formula calculated on the basis of 13 O apfu is Pb 4.01 Te 4+ 2.03 S 6+ 1.97 S 2– 0.98 O 13 . Boevskite is orthorhombic, space group Pnma , with a = 9.7764(7), b = 13.3622(10), c = 10.7213(9) Å, V = 1400.57(19) Å 3 and Z = 4. The strongest lines of the powder X-ray diffraction pattern [ d, Å ( I , %) ( h k l )] are: 6.683 (65) (0 2 0), 3.355 (44) (1 0 3), 3.344 (52) (0 4 0), 3.289 (60) (2 3 0), 3.230 (100) (1 3 2), 3.144 (92) (2 3 1), 3.120 (51) (3 0 1), 2.787 (50) (0 3 3). The crystal structure of boevskite was refined from single-crystal X-ray diffraction data to R 1 = 0.0491 for 1538 reflections with I > 2σ( I ). Boevskite has a unique structure formed by Te–Pb–O layers coplanar to the ac plane with thiosulfate groups and SO 4 tetrahedra located between them. This is the first mineral having both sulfate and thiosulfate groups as species-defining constituents. It is named after the type locality.

Source: Mineralogical Magazine

DOI: 10.1180/mgm.2025.10143