Petewilliamsite
Petewilliamsite is an IMA-recognized mineral species in the arsenate class, with the chemical formula (Ni,Co)₃₀(As₂O₇)₁₅.
It crystallizes in the monoclinic crystal system (space group C2).
Key properties: Mohs hardness 5; specific gravity 4.904; Pale reddish brown to purplish brown streak; Vitreous. Megascopically indistinguishable from brownish purple xanthiosite. R = (470) 9.59, (546) 9.32, (589) 9.27 luster.
IMA symbol Pwi, IMA status: approved, named in 2002.
Known from one specimen; therein the product of oxidation of nickeline.
It is found associated with Xanthiosite, aerugite, paganoite, nickeline, bismuth, bunsenite, rooseveltite, quartz.
The mineral was named to honor geochemist–crystallographer Professor Peter Allan Williams (b. 1950) of the University of Western Sydney, New South Wales, Australia.