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The Mineral romanechite

Botryoidal Black Romanechite

Romanechite is sometimes synonymous with Psilomelane, but in reality Romanechite is a strictly defined mineral that is recognized by the IMA, whereas Psilomelane is not specifically identified, or is a compound of several barium manganse oxides including Romanechite. Romanechite is named after the locality of Romanèche-Thorens in France, the type locality for this mineral.

Chemical Formula

(Ba,H2O)2(Mn4+Mn3+)5O10

Color

Dark gray to black

Crystal System

Monoclinic

Properties

Streak
Black to brownish black
Hardness
5.5 - 6
Transparency
Opaque
Specific Gravity
4.7 - 5
Luster
Submetallic, silky, dull
Cleavage
None
Fracture
Conchoidal, uneven, earthy
Tenacity
Brittle

Crystal Habits

Never in individual crystals. Habits include botryoidal, mammilary, reniform, stalactitic, radiating, acicular, fibrous, dendritic, arborescent, encrusting, massive, and earthy.

Additional Information

Composition
Hydrous barium manganese oxide
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

Uses

Romanechite is an ore of manganese. 

Noteworthy Localities

Romanechite occurs in many manganese deposits, though most often in uninteresting habit and not necessarily identified. The type locality for Romanechite is Romanèche, Saône-et-Loire, France. Other important localities include the Clara Mine, Oberwolfach, Black Forest, Baden-Württemberg, Germany; the Adam Heber Mine, Neustädtel, Schneeberg, Saxony, Germany; and an unspecified locality in Pinal Co, Arizona which has recently been producing nice specimens.

Common Mineral Associations

Barite, Pyrolusite, Quartz, Hematite

Distingushing 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.

romanechite Photos



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