Outstanding reddish brown crystals of the very rare mineral schallerite from the type locality in Franklin (Franklin, Sussex County, New Jersey, United States of America) in a matrix of the same mineral. Ex Vandenbroucke Museum collection from Waregem, Belgium — Photo: David Hospital · CC BY-SA 4.0
Schallerite
Schallerite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₁₆As³⁺₃Si₁₂O₃₆(OH)₁₇.
It crystallizes in the hexagonal crystal system (space group P6_3). It is a member of the Pyrosmalite, Clay structural group.
Key properties: Mohs hardness 5; specific gravity 3.34–3.37; Waxy; pearly on the basal cleavage luster; optically uniaxial.
IMA symbol Slr, grandfathered status — known before the IMA’s founding, named in 1925.
Found in banded willemite-franklinite ore or rhodonite, from a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA); in manganese-rich lenses in quartzitic chlorite schists probably of marine origin (KÄo dnitz Valley, Austria).
It is found associated with Willemite, franklinite, calcite, rhodonite (Franklin, New Jersey, USA); tephroite, pyroxmangite, rhodonite, spessartine, rhodochrosite (KÄo dnitz Valley.
The name refers to Dr. Waldemar Theodore Schaller (1882–1967), mineralogist, U.S. Geological Survey.