Orange microcrystals of the extremely rare mineral braccoite (IMA 2013-093). From: Valletta Mine, Vallone della Valletta, Canosio, Maira Valley, Cuneo Province, Piedmont, Italy. — Photo: David Hospital · CC BY-SA 4.0
Braccoite
Braccoite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaMn²⁺₅[Si₅O₁₄(OH)](AsO₃)(OH).
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Saneroite structural group.
Key properties: specific gravity 3.56; Pale yellow streak; Vitreous to resinous luster; optically biaxial.
IMA symbol Bcc, IMA status: approved, named in 2013.
Found in mineralized quartz veins cutting quartzite.
It is found associated with Tiragalloite, gamagarite, hematite, manganberzeliite, palenzonaite, quartz, saneroite, tokyoite.
The mineral was named to honor Dr. Roberto Bracco (b. 1959), a systematic mineral collector and author with a special interest in manganese minerals.