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Sturmanite

Type Locality
Black Rock Mine, Black Rock, Kalahari manganese field, Northern Cape Province, South Africa
Mineral Data
Ca6(Fe3+,Al,Mn3+)2(SO4)2[B(OH)4](OH)12·25H2O
Strunz: 
7.DG.15
Physical Properties
Crystal System: 
Trigonal
Hardness: 
2.5
Tenacity: 
brittle