Chromatite
A very rare calcium chromate mineral (CaCrO₄) — one of the few minerals built on the chromate ion.
Intro adapted from Wikipedia (CC BY-SA).
Chromatite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CaCr⁶⁺O₄.
It crystallizes in the tetragonal crystal system (space group I4_1/amd). It is a member of the Zircon structural group.
Key properties: specific gravity 3.142; Vitreous luster; optically uniaxial.
IMA symbol Crm, IMA status: approved, named in 1963.
Formed in an arid climate along fractures in limestones and marls by ascending ground water, the chromium derived from underlying bituminous phosphatic marls.
It is found associated with Gypsum, calcite, aragonite, vaterite, portlandite.
As a chromate.