Matthiasweilite, PbTe4+O3, a New Tellurite Mineral from the Delamar Mine, Lincoln County, Nevada, USA

Matthiasweilite (IMA2021-069), Pb2+Te4+O3, is a new mineral discovered at the Delamar mine, Lincoln County, Nevada, USA. It is a secondary mineral, associated with adanite, choloalite, northstarite, and other oxysalts in a quartz-rich matrix, that developed in an altered primary ore along with altaite, tetrahedrite-(Zn), native gold, and other sulfides and selenides. The mineral occurs as tightly intergrown masses of light yellow crystals. The streak is white, luster is adamantine, Mohs hardness is 2½, tenacity is brittle, and fracture is conchoidal; no obvious cleavage is present. The calculated density is 7.282 g/cm3 for the empirical formula. Data from electron probe microanalysis and assuming O = 3 gives the empirical formula Pb0.99Te4+1.01O3. Matthiasweilite is triclinic, space group P, with cell parameters a = 7.0256(4), b = 10.6345(6), c = 11.9965(8) Å, α = 78.513(6), β = 83.104(6), γ = 84.083(6)°, V = 869.10(9) Å3, and Z = 10. The crystal structure (R1 = 0.0523 for 3416 I > 2σI reflections) consists of Te4+O3 trigonal pyramids that are linked via relatively short (<2.6 Å) Pb–O bonds to form a framework.