Hjalmarite

amphibole

hjalmarite

rhodonite

manganese

Images

Formula: Na(NaMn)Mg₅Si₈O₂₂(OH)₂
Inosilicate (chain silicate), amphibole, manganese-bearing mineral
Specific gravity: 3.0 measured, 3.123 calculated
Hardness: 5 to 5½
Colour: Grey-white
Luminescence: No fluorescence under UV
Environments

Metamorphic environments

Hjalmarite is a relatively new mineral, approved in 2017.

Localities

At the type locality, the Långban Mine, Långban Ore District, Filipstad, Värmland County, Sweden, hjalmarite was discovered in manganese skarn, closely associated with mainly rhodonite and quartz. It is greyish white with vitreous lustre and non-fluorescent. The crystals are up to 5 mm in length.
The hjalmarite-bearing skarn formed at peak regional metamorphism, at temperature 600^oC or higher (EJM 31.565-574).

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