Manganite Composition, Crystallization & Structure

Composition. Mn O(OH) or  Mn2O3.H2O = Oxygen 27.3, manganese 62.4, water 10.3

Crystallization. Orthorhombic. Crystals usually long prismatic with obtuse terminations, deeply striated vertically (Fig. B, pl, VII). Often twinned.

Structure. Usually in radiating masse; crystals often grouped in bundles. Also columnar.

Physical Properties. Perfect cleavage parallel to brachypinacoiod. H. = 4.  G. = 4.3. Metallic luster. Steel-gray to iron-black color. Dark brown streak.

Test. infusible. A small amount of the powdered mineral gives in O.F. a reddish violet bead with borax or a bluish green opaque bead with sodium carbonate. Much water when heated in C.T. Told chiefly by its black color prismatic crystals, hardness (4) and brown streak. The last two will serve to distinguish it from pyrolusite.

Occurrence. Found associate with other manganese oxides and has a similar origin. It frequently alters to pyrolusite. Found often in veins associated with the acid igneous rocks, both as filing cavities and as a replacement of the neighboring rocks. Barite and calcite are frequent associates. Occurs at Ilfeld, Harz Mountains, in fine crystals; also at Ilmenau, Thuringia; Cornwall, England; Negaunee, Michigan, etc. In Nova Scotia.

Use. a minor ore of manganese.