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Schwertmannite (Rare species and systematic collections) Fe16+3O16(OH)12(SO4)2 tetragonal Finland, Oulu, Pyhäsalmi Mine “The purest sample found to date is from the Pyhäsalmi base-metal mine, Province of Oulu, Finland (type locality), at which schwertmannite occurs as crusts on stones inundated by acidic drainage from a mound of concentrate sand.1 The mineral is found “As fibrous aggregates of poorly-crystalline needles, to 100 μm, in films and thin to thick crusts.”1 “The mineral is known synthetically and from more than 40 localities in Europe, North America and Australia (unspecified). All occurrences are related to the surface or near-surface oxidation of metal sulfides; optimum conditions for formation are pH 3-4.5 and SO4 concentrations of 1000-3000mg/L. Typical associations are jarosite, natrojarosite, goethite, and ferrihydrite. The new name is for Udo Schwertmann (b.1927), Technical university of Munich. Cotype specimens are in the Geological Museum, University of Helsinki, Finland.”2 The mineral is obviously not a rare one, but it is certainly not one of interest to most collectors. If you want to get specimens of this material the authors of the original description should probably be consulted. They may still have access to specimens from the the Pyhäsalmi mine and the 20 unspecified localities that they site. Some rare mineral dealers may also carry specimens of this material. I would imagine that the demand for this mineral is not brisk. 1. Handbook of Mineralogy, Volume III, , Anthony, Bideaux, Bladh, Nichols, p501. 2. J.M. Bigham, L. Carlson, E. Murad (1994) Schwertmannite, a new iron oxyhydroxysulphate from Pyhäsalmi, Finland, and other localities. Mineral. Mag., 58, 641-648. (American Mineralogist abstract Vol 80, July-August 1995 p. 847.
In the late 19th and early 20th centuries, the mine was worked for silurian alum shales used as a raw material for the production of sulphuric acid. Around 1915, in order to preserve the coloured sulphate sinters formed by decomposition of pyrite and marcasite, the underground workings were transformed into a visitor's grotto. Located at Garnsdorf, 2 km SW of Saalfeld.