Morrisonite
Morrisonite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ca₁₁(As³⁺V⁴⁺₂V⁵⁺₁₀As⁵⁺₆O₅₁)₂·78H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 2.5; specific gravity 2.29; Grayish blue streak; Vitreous luster; optically biaxial.
IMA symbol Mris, IMA status: approved, named in 2014.
Forms secondarily through oxidation of montroseite-corvusite assemblages in a moist environment.
It is found associated with Gatewayite, packratite, vanarsite, pharmacolite, montroseite, corvusite.
The name refers to the Morrison Formation, in which the Packrat mine and other U-V mines of the Uravan mineral belt occur.
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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