Parasymplesita and arseniosiderite. Carlés gold mine, Salas, (Asturias) Spain — Photo: Bergminer · CC BY-SA 4.0
Parasymplesite
Parasymplesite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Fe²⁺₃(AsO₄)₂·8H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Vivianite structural group.
Key properties: Mohs hardness 2–3; specific gravity 3.07–3.12; Very pale blue or green streak; Vitreous to waxy luster; optically biaxial.
IMA symbol Psym, grandfathered status — known before the IMA’s founding, named in 1954.
A rare secondary mineral found in the oxide zone of some arsenic-rich hydrothermal base-metal mineral deposits.
It is found associated with Symplesite, köttigite, pharmacosiderite, scorodite, arsenopyrite, löllingite.
Its name comes from the Greek para, for near, and its dimorphous relation to symplesite.