Beaverite-(Cu) on Siderite ''cast'' after Gypsum (RARE locality specimen)

Item Description

Here we have a remarkably rare specimen from the Pioche District in Nevada, featuring green micro aggregates of Beaverite-(Cu), which is a member of the Alunite Group that are partially coating a hollow "cast" of brown Siderite which formed over a preexisting crystal of Gypsum that has since been dissolved away. I can only remember having one other piece of this material to offer in the auctions, so if you collect rarities, pseudomorphs/''casts'' or just unusual locality pieces, don't miss out on this one.
Ex Kay Robertson Collection (#10992). Kay was a prominent California collector, who specialized in European classics. She nearly lived 100 years from April 1920 - March 2020. See the article in the March-April, 2007 Mineralogical Record ( https://www.mineralogicalrecord.com/pdfs/Kay%20Robertson%20Collection.pdf ), and the 50+ page article in the German Magazine "Mineralien Welt" November-December 2017.