Allactite is an unusual manganese arsenate hydroxide that was first described in 1884, from the little-known but mineralogically interesting Moss mine at Nordmark, Filipstad, Värmland, Sweden. It was subsequently, rather rapidly found at the better known Långban deposit 8 miles to the east-northeast and then at several other mines in the Nordmark Mining Field and Harstigen mine at Pajsberg, as well as at Franklin and Sterling Hill in New Jersey, USA. It does, however, remain an extremely rare species which is rarely available for sale from any locality. This fine miniature specimen from the Långban occurrence is from the comprehensive systematic collection assembled by the brothers Martin and Michael Günther (1951-2007 & 1956-2021). It features reddish brown Allactite microcrystals lining a Calcite-filled cavity running across the specimen. Some of the Calcite has come away to uncover Allactite which appears to continue underneath the Calcite across the middle of the specimen.
