Bettertonite
A white hydrated aluminium arsenate named for John Betterton, museum geologist at Haslemere Educational Museum in Surrey.
Intro adapted from Wikipedia (CC BY-SA).
Bettertonite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Al₆(AsO₄)₃(OH)₉(H₂O)₅·11H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: specific gravity 2.02; White streak; Vitreous to pearly, somewhat silky luster; optically biaxial.
IMA symbol Bet, IMA status: approved, named in 2014.
Extremely rare, in quartz veins in a multi-stage, polymetallic hydrothermal deposit; probably formed from leaching and the replacement of Al to Fe in pharmacosiderite.
It is found associated with Arsenopyrite, chamosite, liskeardite, penberthycroftite, pharmacoalumite, pharmacosiderite, brochantite, chalcopyrite, cassiterite.
The mineral was named to honor Mr. John Betterton (b. 1959) a museum geologist/mineralogist at Haslemere Educational Museum, Haslemere, Surrey, England.