THE MINERAL MANGANITE

Chemical Formula: MnO(OH), Manganese Oxide Hydroxide
Class: Oxides and Hydroxides
Uses: A minor source of manganese and as a mineral specimen
Specimens

Manganite was a valuable manganese ore when it was found in plentiful deposits. Now its rarity has relegated it to the standing of a minor ore dispite its high manganese content. Crystals are the chief indicator for identification. Only a few metallic minerals will have similar crystals (such as enargite) and these can be eliminated by means of comparing manganite's reddish streak and hardness. Pyrolusite is softer and has a bluish streak. If manganite is massive, it is difficult to distinguish it from other manganese minerals. Fine crystals of manganite can make a nice addition to a mineral collection.

PHYSICAL CHARACTERISTICS:

Color is black to steel gray.
Luster is metallic to dull in weather specimens.
Transparency: Crystals are opaque, translucent in only thin splinters.
Crystal System is monoclinic; 2/m
Crystal Habit is typically short prismatic crystals that have a psuedo-orthorhombic shape. The terminations are generally blunted with domes and minor pyramid faces. The crystals are striated lengthwise. Crystals are usually grouped into tight bundles and columnar, massive and fiberous forms are also known. Penetration and contact twinning does occassionally occur.
Cleavage is perfect in one direction lengthwise and good to fair in two other directions, one lengthwise at near right angles to the first one and one basal.
Fracture is uneven.
Hardness is 4
Specific Gravity is 4.3 (average for metallic minerals)
Streak is reddish to brownish black.
Associated Minerals are calcite, barite, garnets, limonite, siderite, pyrolusite and other manganese minerals.
Other Characteristics: Alters to pyrolusite which can coat the crystals, dulling the luster and can affect a streak test.
Notable Occurrences include Cornwall, England; Harz Mts., Germany; China; Sterling Hill, New Jersey and Negaunee, Michigan, USA and Ukraine.
Best Field Indicators are crystal habit, luster, striations, color and streak.