Original paper

Lead-antimony sulfosalts from Tuscany (Italy). I. Scainiite, Pb14Sb30S54O5, the first Pb-Sb oxy-sulfosalt, from Buca della Vena mine

Orlandi, Paolo; Moëlo, Yves; Meerschaut, Alain; Palvadeau, Pierre

European Journal of Mineralogy Volume 11 Number 6 (1999), p. 949 - 954

21 references

published: Nov 29, 1999
manuscript accepted: Jul 12, 1999
manuscript received: Feb 12, 1999

DOI: 10.1127/ejm/11/6/0949

BibTeX file

ArtNo. ESP147051106004, Price: 29.00 €

Download preview PDF Buy as PDF

Abstract

Abstract The new mineral scainiite, Pb14Sb30S54O5, the first lead oxy-sulfosalt, has been found at Buca della Vena mine in the Apuan Alpes, northern Tuscany, Italy. Scainiite occurs as black acicular crystals with bluish metallic lustre, elongated [010], up to 2 mm long and 0.2 mm thick. The mineral is brittle, opaque; VHN20= 192 kg/mm2, dcalc = 5.56 g/cm3. In reflected light it shows a low anisotropy and bireflectance, and rare red internal reflections. Its ideal chemical formula, derived from electron-microprobe data and from crystal structure refinement, is Pb14Sb30S54O5. Scainiite is monoclinic, space group C2/m, a = 52.00(2), b = 8.148(2), c = 24.31(6) Å, β = 104 09(4)°, Z = 4. The strongest five lines of the X-ray powder diffraction pattern are [d in Å(I)(hkl)]: 3.472(100)(1̅4̅ 0 4), 2.956(54) (6 2 4, 12 2 1), 2.052(46)1̲4̲ 0 8, 2̅4̅ 0 1), 3.041(35)(4̅ 0 8), 2.228(22)(2̅2̅ 0 1, 22 0 6, 8̅ 2 9). Scainiite is a structural derivative of synthetic hexagonal Ba~12Bi-24S48, a member of cyclically twinned sulfosalt structures (zinkenite group). Scainiite crystallized in small fractures of dolomitic lenses in massive Fe-Ba ore, together with many Pb-Sb sulfosalts. The formation of this unique lead oxy-sulfosalt is related to narrow fO2 - fS2 conditions, corresponding to the magnetite-hematite-pyrite buffer at relatively high temperature (> 300°C).

Keywords

scainiitenew mineral speciessulfosaltleadantimonyoxy-sulfideTuscanyItaly.