Lorándite
A red thallium-arsenic sulfosalt — rare, but still the most common thallium mineral, occurring in gold and mercury deposits.
Intro adapted from Wikipedia (CC BY-SA).
Lorándite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula TlAsS₂.
It crystallizes in the monoclinic crystal system (space group P2_1/a).
Key properties: Mohs hardness 2–2.5; specific gravity 5.53; Cherry-red streak; Metallic, adamantine luster; optically biaxial.
IMA symbol Lor, IMA status: approved, named in 1894.
Although rare, the most widespread thallium mineral; of hydrothermal origin, typically formed at relatively low temperatures.
It is found associated with Stibnite, realgar, orpiment, cinnabar, vrabite, greigite, marcasite, pyrite, tetrahedrite, antimonian sphalerite, arsenic, barite.
The name refers to Eötvös Lorand (1848–1919), physicist of Budapest, Hungary.