Allochalcoselite
Allochalcoselite is an IMA-recognized mineral species in the halide class, with the chemical formula Cu¹⁺Cu²⁺₅PbO₂(SeO₃)₂Cl₅.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 3–4; specific gravity 4.61; Brown streak; Adamantine luster; optically biaxial.
IMA symbol Acc, IMA status: approved, named in 2004.
Formed by sublimation around a degassing volcanic fumarole.
It is found associated with Cotunnite, sophiite, ilinskite, georgbokiite, burnsite.
Derived from the Greek for “different” (allos) and “copper” (chalkos) and from “selenium”, to reflect the different valences and crystallographic behavior of copper in this selenite mineral.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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