Pyrolusite Composition, Crystallization & Structure

Composition. Manganese dioxide, MnO2. Commonly contains a little water.

Crystallization. Crystals probably always pseudomorphous after manganite.

Structure. Readiting columnar to fibrous (Fig. A, pl. VII); also granular massive; often in reniform coats.

Physical Properties. H. = 2-2.5 (Often soiling the fingers). G. = 4.75. Metallic luster. Iron-black color and streak. Splintery fracture.

Test. infusible. A small amount of powdered mineral gives in O.F. as reddish violet bead with borax or a bluish green opaque bead with sodium carbonate. Gives oxygen in C.T., which will cause a splinter of charcoal to ignite when placed in tube above the mineral and heated. Only a small amount of water in C.T. In hydrochloric acid, chlorine gas evolved.

Occurrence. A secondary mineral. Manganese is dissolved out of the crystalline rocks, in which it is almost always present in small amounts, and redeposited under various conditions, chiefly as pyrolusite. Dendritic coating of pyrolsite are frequently observed on rock surfaces, coating pebbles, etc. Nodular deposits of pyrolusite. Are frequently observed on rock surfaces, coating pebbles, etc. Nodular deposits of pyrolusite are found on the sea bottom. Nests and beds of manganese ores are found enclosed in residual clays, derived from the decay of manganiferous limestones. It is thought that manganese oxides were originally colloidal in character, having subsequent to deposition assumed a crystalline form. Also found in veins with quartz and various metallic minerals.

Pyrolusite is a common mineral, widespread in its occurrence. Mined in Thuringia, Moravia, Transylvania, Bohemia, Westphalia, Australia, Japan, India, Brazil, New Brunswick, Nova Scotia. In the United States, manganese ores are found in Virginia, Georgia, with the hematite ores of the Lake Superior districts, in Arkansas and California.

Name. Pyrolusite is derived from two Greek words meaning fire and to wash, because it is used to free glass through its oxidizing effect of the colors due to iron.

Uses. Most important manganese ore. Manganese is used in the manufacture of the alloys with iron, spiegeleisen and ferromanganese, employed in making steel; also in various alloys with copper, zinc, aluminum, tin, lead, etc. Pryrolusite is used as an oxidizer in the manufacture of chlorine, bromine and oxygen; as a disinfectant in potassium permanganate; as a drier in paints, a decolorizer of glass, and in electric cells and batteries. Manganese is also used as a coloring material in bricks, potteries. Manganese is also used as a coloring material in bricks, pottery, glass, etc.

Polianite, MnO₂, is a rare mineral, occurring in minute tetragonal crystals.