Philoxenite
A very rare thallium-lead-arsenic sulfosalt of low-temperature hydrothermal veins.
Intro adapted from Wikipedia (CC BY-SA).
Philoxenite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (K,Na,Pb)₄(Na,Ca)₂(Mg,Cu)₃(Fe³⁺₀.₅Al₀.₅)(SO₄)₈.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 3; specific gravity 2.732; White streak; Vitreous luster; optically biaxial.
IMA symbol Pxn, IMA status: approved, named in 2015.
Forms as a sublimate at an active volcanic fumarole.
It is found associated with Euchlorine, langbeinite, hematite, tenorite, piypite, alumoklyuchevskite, dolerophanite, vergasovaite, cupromolybdite, ziesite, yaroshevskite.
The name comes from the ancient Greek for ‘friend’, and ‘guest’.