Juansilvaite is a very rare, complex arsenate-sulfate mineral with formula Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O.Kampf, A.R., Nash, B., Dini, M., and Molina Donoso, A.A., 2015. Juansilvaite, IMA 2015-080. CNMNC Newsletter No. 28, December 2015, page; Mineralogical Magazine 79, 1859–1864 It is both hydroxyarsenate and dihydroxyarsenate. It is among few relatively new minerals from the Torrecillas mine in Chile, the other being torrecillasite, canutite, chongite, gajardoite, leverettite, and magnesiokoritnigite. Although having quite common among minerals space group C2/c, juansilvaite has a new type of structure.
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