Image of the brattforsite (arrow points to the largest aggregate) type specimen with jacobsite (black) and calcite (whitish), GEO-NRM #19100303. Inset image shows a detail on the specimen (red frame). The image is published in an open access article (Brattforsite, Mn19(AsO3)12Cl2, a new arsenite mineral related to magnussonite, from Brattforsgruvan, Nordmark, Värmland, Sweden: https://link.springer.com/article/10.1007/s00710-021-00749-9 ) distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( https://creativecommons.org/licenses/by/4.0/ ). — Photo: Torbjörn Lorin · CC BY 4.0
Brattforsite
Brattforsite is an IMA-recognized mineral species in the halide class, with the chemical formula Mn₁₉As₁₂O₃₆Cl₂.
It is a member of the Magnussonite structural group.
Key properties: Mohs hardness 3–4; specific gravity 4.49; White streak; Resinous to vitreous luster; optically biaxial.
IMA symbol Bf, IMA status: approved, named in 2020.
Probably replaced a Mn-rich precursor mineral in mineralized skarn due to alteration by a late- or post-metamorphic, As and Cl-bearing fluid.
It is found associated with Jacobsite, alleghanyite, phlogopite, calcite, dolomite.
The name refers to the mine that produced the studied material.