Colorless crystals of the extremely rare thallium mineral lanmuchangite from the second known locality for the mineral, the famous thallium deposit of Allchar (Crven Dol Mine, Allchar, Roszdan, Macedonia), associated to red realgar. Lanmuchangite is a thallium aluminium sulphate. PXRD and EDS analyzed. — Photo: David Hospital · CC BY-SA 4.0
Lanmuchangite
Lanmuchangite is an IMA-recognized mineral species in the sulfate class, with the chemical formula TlAl(SO₄)₂·12H₂O.
It crystallizes in the cubic crystal system (space group Pa3). It is a member of the Alum structural group.
Key properties: Mohs hardness 3.1–3.4; specific gravity 2.22; White streak; Vitreous luster.
IMA symbol Lmh, IMA status: approved, named in 2001.
Found in the oxidation zone of a Tl–Hg deposit.
It is found associated with Melanterite, pickeringite, jarosite, gypsum, potassium alum, arsenolite, sulfur.
The name refers to its occurrence in the Lanmuchang deposit, China.