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Psilomelane describes barium manganese hydroxides that do not form in visible crystals. Originally recognized as an individual mineral species, Psilomelane was discredited by the IMA in 1982. However, the name is still in use today, describing manganese hydroxides such as Romanechite and Hollandite that are not specifically identified and sometimes even admixed together.
Psilomelane can be banded with Pyrolusite, with alternating layers of light and dark gray bands. It is named after the Green term " psilos", meaning smooth, and " melas", meaning black. |
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Chemical Formula |
BaMn2+Mn4+8O16(OH)4 |
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Composition |
Barium manganese hydroxide |
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Color |
Dark gray to black |
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Streak |
Black to brownish black |
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Hardness |
5 - 6 |
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Crystal System |
Monoclinic |
Crystal Forms
and Aggregates |
Does not occur in individual crystals. Habits include botryoidal, mammilary, reniform, stalactitic, dendritic, arborescent, encrusting, massive, and earthy. |
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Transparency |
Opaque |
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Specific Gravity |
4.5 - 4.7 |
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Luster |
Submetallic, dull |
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Cleavage |
None |
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Fracture |
Conchoidal, uneven, earthy |
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Tenacity |
Brittle |
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In Group |
Oxides; Hydroxides |
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Striking Features |
Color, streak, and association with other manganese minerals |
| Environment |
As a secondary mineral in hydrothermal replacement deposits, in sandstones, limestones, and clays. |
| Rock Type |
Sedimentary, Metamorphic |
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Popularity (1-4)
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3 |
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Prevalence (1-3)
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2 |
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Demand (1-3) |
2 |
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Psilomelane is an ore of manganese. The banded form combined with Pyrolusite is sometimes polished as a collectors species and as a minor gemstone.
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Psilomelane occurs in many manganese deposits worldwide, often in uninteresting forms. Only few localities have produced any remarkable specimens. Fuzzy, hair-like masses associated with Pyrolusite form a very unique habit from the Tower mine, Luis Lopez Manganese District, Socorro Co., New Mexico. Specimens have also been found in Taouz, Er Rachidia Province, Morocco; Ironwood, Gogebic County, Michigan; Bisbee, Cochise Co., Arizona; and Austinville, Wythe Co., Virginia.
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Pyrolusite - Most commonly in crystallized aggregates, which are lacking in Psilomelane.
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