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Manganite Specimens
Manganite's composition is manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic).
Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped together in bundles.
The color is dark steel-grey to iron-black, and the luster brilliant and submetallic. The streak is dark reddish-brown. The
hardness is 4, and the specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect
cleavage parallel to the prism faces. Twinned crystals are not infrequent. The mineral contains 89.7%
manganese sesquioxide; it dissolves in hydrochloric acid with evolution of chlorine.
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Impressive "chunk" of manganite with acicular crystals from the South Jackson Mine in Negaunee, Mi. Approx. size:
64x52x30 Weight: 208.9 gm.
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This is really a special piece of manganite with small balls of barite all over one surface. There's also a pretty
impressive vein of acicular crystals running all around the specimen. Collected at the South Jackson Mine, Negaunee,
Mi. Approx. size: 48x40x33 Weight: 181.4 gm.
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