Psilomelane, now scientifically known as romanechite, is a hard, black manganese oxide typically found in botryoidal or stalactitic forms. It is easily identified by its smooth, mammillary surface texture and heavy weight. Collectors highly prize high-quality, polished botryoidal specimens for their unique, grape-like clusters.
Is this psilomelane?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch psilomelane with a known reference. Psilomelane sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish black.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: black, bluish-black, gray, iron black, dark steel gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: botryoidal, mammillary, reniform.
Often confused with
Psilomelane vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Psilomelane leaves brownish black, Pyrolusite leaves black, bluish black; luster reads submetallic on Psilomelane and metallic on Pyrolusite.
How to tell apart: Psilomelane is noticeably harder (Mohs 5-6 vs. 4); streak differs, so Psilomelane leaves brownish black, Manganite leaves reddish brown to nearly black.
How to tell apart: Luster reads submetallic on Psilomelane and imperfect adamantine metallic to dull earthy; silky when fibrous on Goethite.
Often found alongside psilomelane
Minerals reported to co-occur with psilomelane. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ba,H₂O)₂Mn₅O₁₀
- Mohs hardness
- 5-6
- Density
- 4.4-4.7 g/cm³
- Colors
- Streak
- Brownish black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Botryoidal, mammillary, reniform
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Ore of manganese
- Host rock
- General term for hard, black Mn oxides
Where rockhounds find psilomelane
4 mapped spotsClassic worldwide localities
- Romanèche-Thorins, France
- Sterling Hill, New Jersey
- Germany
- Mexico
- Arizona, USA
Field-hunting tip
Where it forms: General term for hard, black Mn oxides. If you start seeing pyrolusite, manganite, barite in float, you are in the right ground. Typical habit: botryoidal, mammillary, reniform. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, Idaho, West Virginia. Start trip planning there.
Common questions
How do you identify psilomelane?+
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Can I find psilomelane in the United States?+
What rocks look like psilomelane?+
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Find psilomelane on the map
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