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Formula: CaMg7Fe3+2(OH)18(SO4)2.12H2O
Sulphate, wermlandite group
Crystal System: Trigonal
Specific gravity: 2.02 calculated
Colour: Colourless
Environments
Erssonite is a new mineral, approved in 2021 and to date (March 2023) reported only from the type locality.
Localities
At the type locality, the Långban mine, Långban Ore District, Filipstad, Värmland County, Sweden, erssonite was
discovered in a late-stage, low-temperature assemblage in cavities of a
magnetite-bearing dolomitic rock.
Associated minerals include dolomite,
calcite, members of the
magnetite–magnesioferrite
solid-solution series, phlogopite,
chrysotile, pyroaurite and
norbergite. Erssonite forms colourless, platy hexagonal crystals up to
10 μm thick
(MM 85.5.817-826).
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