Applied to material from Långban, Sweden with a sphenoidal habit. Presumably identical to manganite.
References for Sphenomanganite
Reference List:
Flink (1919), Geol. För. Förh.: 41: 329.
Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 646.