Cuyaite
Cuyaite is an IMA-recognized mineral species in the halide class, with the chemical formula Ca₂Mn³⁺As³⁺₁₄O₂₄Cl.
Key properties: Mohs hardness 2.5; specific gravity 4.14; White or very pale brown streak; Adamantine, silky (parallel aggregates) luster; optically biaxial.
IMA symbol Cuy, IMA status: approved, named in 2020.
Formed by the oxidation of As-bearing primary phases and alteration by saline fluids derived from evaporating meteoric water under hyperarid conditions and perhaps assisted by regional coastal fog.
It is found associated with Anhydrite, native arsenic, arsenolite, calcite, claudetite, ferrinatrite, gajardoite-3R, leiteite, magnesiocopiapite, phosphosiderite, pyrite, realgar.
The name refers to a town near the type locality, Cuya, Arica Province, Chile.