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Formula: Sb5+Mn3+(Mg,Mn2+)10O8(BO3)4
Oxyborate, pinakiolite
group,
antimony- and manganese-
bearing mineral
Crystal System: Monoclinic
Specific gravity: 4.14 calculated
Hardness: 6
Streak: Reddish brown
Colour: Black to dark reddish brown
Luminescence: Not fluorescent under UV
Environments
Folkivite was approved in 2016, but to date (May 2023) it has been reported only from the type locality.
Localities
At the type locality, the Kitteln mine, Nordmark Odal Field, Filipstad, Värmland County, Sweden, folvikite is
an oxyborate occurring as a
primary
skarn mineral embedded in
calcite. It forms black to dark reddish brown striated prismatic crystals
up to 0.3 mm. Associated minerals include hausmannite,
tegengrenite, and a magnesium-dominant analogue of
sonolite or jerrygibbsite
(MM 82.4.821–836).
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