Erssonite

erssonite

magnesioferrite

pyroaurite

norbergite

Images

Formula: CaMg₇Fe³⁺₂(OH)₁₈(SO₄)₂.12H₂O
Sulphate, wermlandite group
Crystal System: Trigonal
Specific gravity: 2.02 calculated
Colour: Colourless
Environments

Metamorphic environments

Erssonite is a new mineral, approved in 2021 and to date (July 2025) 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).
Erssonite from the Långban Mine - Image

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