Reddish orange crystal aggregates of the rare Mn-arsenate mineral arseniopleite from the TL in Sweden (Sjögruvan, Grythyttan, Hällefors, Örebro County, Sweden). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Arseniopleite
Arseniopleite is an IMA-recognized mineral species in the arsenate class, with the chemical formula NaCaMnMn₂(AsO₄)₃.
It crystallizes in the monoclinic crystal system (space group I2/a). It is a member of the Alluaudite structural group.
Key properties: Mohs hardness 3–4; specific gravity 4.17–4.22; Yellowish brown streak; Dull luster; optically uniaxial.
IMA symbol Apl, IMA status: approved, named in 1888.
Occurs as fracture fillings and thin veins in banded dolostone (Sjö mine, Sweden); in a metamorphosed Fe-Mn orebody (Långban, Sweden).
It is found associated with Rhodonite, tephroite, hedyphane, dolomite, calcite (Sjö mine, Sweden); calcite, berzeliite, kutnohorite, sarkinite, gonyerite, katoptrite (Långban, Sweden).
The name comes from arsenic and the Greek for more, as it added to the number of related minerals previously described.