Borate, oxyborate, pinakiolite group
Specific gravity: 4.14 calculated
Streak: Reddish brown
Colour: Black to dark reddish brown
Luminescence: Not fluorescent in UV
Folkivite was approved in 2016, but to date (June 2022) it has been reported only from the type locality.
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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