MANGANITE  , a

mineral consisting of hydrated manganese sesquioxide, Mn20a•H20,crystallizing in the orthorhombic system and isomorphous with diaspore and gothite . Crystals are prismatic and deeply striated parallel to their length; they are often grouped together in bundles . The colour is dark steel-grey to iron-black, and the lustre brilliant and submetallic: the streak is dark reddish-brown . The hardness is 4, and the specific gravity 4.3 . There is a perfect cleavage parallel to the brachypinacoid, and less perfect cleavage parallel to the prism faces m . Twinned crystals are not infrequent . The mineral contains 89'7% of manganese sesquioxide; it dissolves in hydrochloric acid with evolution of chlorine . The best crystallized specimens are those from Ilfeld in the Harz, where the mineral occurs with calcite and barytes in veins traversing porphyry . Crystals have also been found at Ilmenau in Thuringia, Neukirch near Schlett- stadt in Alsace (" newkirkite "), Granam near Towie in Aberdeenshire, Upton Pyne near Exeter and Negaunee in Michigan . As an ore of manganese it is much less abundant than pyrolusite or psilomelane . The name manganite was given by W . Haidinger in 1827: French authors adopt F .

S .

Beudant's name " acerdese," (Gr . &Keptrls, unprofitable) because the mineral is of little value for bleaching purposes as compared with pyrolusite . (L . J .