Wiklundite
An extraordinarily complex lead-manganese arsenite-silicate with a huge unit cell.
Intro adapted from Wikipedia (CC BY-SA).
Wiklundite is an IMA-recognized mineral species in the silicate class, with the chemical formula Pb₂(Mn²⁺,Zn)₃(Fe³⁺,Mn²⁺)₂(Mn²⁺,Mg)₁₉(As³⁺O₃)₂[(Si,As⁵⁺)O₄]₆(OH)₁₈Cl₆.
It crystallizes in the hexagonal crystal system (space group R-3c).
Key properties: specific gravity 4.072; Pale yellowish brown streak; Resinous to submetallic luster; optically uniaxial.
IMA symbol Wik, IMA status: approved, named in 2015.
Found in a Fe-Mn-(Ba-As-Pb-Sb) deposit in dolomite-rich skarn, probably formed shortly after peak metamorphism at temperatures above 600° C and pressures < 3.5 kbars.
It is found associated with Tephroite, mimetite, turneaureite, johnbaumite, jacobsite, barite, native lead, filipstadite, parwelite, manganiferous calcite.
The mineral was named to honor Swedish mineral collectors Markus Wiklund (b.1969) and Stefan Wiklund (b. 1972), the brothers who jointly found the specimen containing the mineral.