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Rounded Stalactitic Psilomelane

The Mineral psilomelane




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.
Chemical Formula BaMn2+Mn4+8O16(OH)4
Composition Barium manganese hydroxide
Color Dark gray to black
Streak Black to brownish black
Hardness 5 - 6
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.
Transparency Opaque
Specific Gravity 4.5 - 4.7
Luster Submetallic, dull
Cleavage None
Fracture Conchoidal, uneven, earthy
Tenacity Brittle
In Group Oxides; Hydroxides
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
Popularity (1-4) 3
Prevalence (1-3) 2
Demand (1-3) 2


Psilomelane ON EBAY



USES
Psilomelane is an ore of manganese. The banded form combined with Pyrolusite is sometimes polished as a collectors species and as a minor gemstone.

NOTEWORTHY LOCALITIES
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.

COMMON MINERAL ASSOCIATIONS
Barite, Pyrolusite, Quartz, Hematite

DISTINGUISHING SIMILAR MINERALS
Pyrolusite - Most commonly in crystallized aggregates, which are lacking in Psilomelane.
Hematite - Has a red streak.
Goethite - Yellow streak, lower specific gravity, usually a darker color.


psilomelane PHOTOS
 
ADDITIONAL RESOURCES
 
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