Psilomelane
Rock made of romanèchite, hollandite
Common · (Ba,H₂O)₂Mn₅O₁₀ (mainly)
An obsolete field name, from the Greek for "smooth black", for hard black botryoidal masses of manganese oxides, now known to be mixtures, mostly of romanechite with hollandite and others. Harder than pyrolusite and manganite, with a brownish black streak. Long a common and important manganese ore, mined with pyrolusite for the same uses.
Rock
- Kind of rock
- Chemical sedimentary rock
- Deposits
- Oxidized zone (gossan)
- Metals
- Manganese
- How it forms
- Black manganese oxides that form where manganese-rich deposits oxidise, as black gossans.
- Uses
- Ore of manganese.
Identity
- Formula
- (Ba,H₂O)₂Mn₅O₁₀ (mainly)
- Chemical class
- Oxide
- Also known as
- Black hematite (misnomer)
- Ore of
- Manganese
Crystallography
- Crystal system
- Amorphous
- Habits
- Botryoidal, Stalactitic, Massive
- Fracture
- Uneven
Physical properties
- Mohs hardness
- 5.5
- Density
- 4.2 g/cm³
- Luster
- Submetallic, Dull
- Colors
- black, iron-black, steel gray
- Streak
- brownish black
- Transparency
- Opaque
Geology
- Origins
- Sedimentary
- Host rocks
- Limestone and chalk
- Associated minerals
- Pyrolusite, Manganite, Braunite, Goethite, Calcite, Quartz, Barite
- Geography
- England (Restormel mine, Cornwall; Brendon Hills, Somerset), Scotland (Hoy, Orkney), Germany (Sayn, near Koblenz), USA (Crimora, Virginia; Arkansas; Vermont), Canada (Nova Scotia), South Africa (Hout Bay)
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Psilomelane. Wikipedia.
- Romanèchite. Wikipedia.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Romanèchite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
- Gossan. Wikipedia.
- C. R. Hallsworth, R. W. O’B. Knox, BGS Rock Classification Scheme, Volume 3: Classification of sediments and sedimentary rocks (Research Report RR 99-03). British Geological Survey, 1999.
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