Kegginite
A very rare phosphate known from a single level of Colorado's Packrat mine.
Intro adapted from Wikipedia (CC BY-SA).
Kegginite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Pb₃Ca₃[AsV₁₂O₄₀(VO)]·20H₂O.
It crystallizes in the hexagonal crystal system (space group P-3).
Key properties: Mohs hardness 2; specific gravity 2.69; Pinkish orange streak; Vitreous luster; optically uniaxial.
IMA symbol Kgn, IMA status: approved, named in 2015.
A secondary mineral found on asphaltum in a montroseite- and corvusite-bearing sandstone in a roll-front type uranium deposit.
It is found associated with Ansermetite, gypsum, mesaite, sherwoodite.
Recognizes the presence of the e-isomer of the Keggin anion in the mineral and also honors J.F. Keggin who first experimentally determined the structure of α-Keggin anions in 1934.