Stilpnomelane is a phyllosilicate mineral typically found in metamorphosed iron-rich rocks and low-grade metamorphic schists. It is easily recognized by its dark, bronzy to black color and distinctive platy or foliated habit, which resembles common micas but with a more brittle structure.
Is this stilpnomelane?
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 stilpnomelane with a known reference. Stilpnomelane sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly to vitreous on cleavage surface, may be submetallic.
- 4Match the color rangeCompare against the expected color range: black, brown red, green, golden brown.
- 5Look at form & habitCrystal system: triclinic. Typical habit: fibrous, foliated, platy.
Often confused with
Stilpnomelane vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Stilpnomelane leaves gray white, Biotite leaves white; luster reads pearly to vitreous on cleavage surface, may be submetallic on Stilpnomelane and splendent to submetallic, vitreous, pearly on cleavage on Biotite.
How to tell apart: Streak differs, so Stilpnomelane leaves gray white, Chlorite leaves white.
How to tell apart: Streak differs, so Stilpnomelane leaves gray white, Muscovite leaves white; luster reads pearly to vitreous on cleavage surface, may be submetallic on Stilpnomelane and vitreous to pearly or silky on Muscovite.
Often found alongside stilpnomelane
Minerals reported to co-occur with stilpnomelane. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₄Fe₄₈[Si₆₄Al₈]O₁₆₄(OH)₅₂·nH₂O
- Mohs hardness
- 3-4
- Density
- 2.59-2.96 g/cm³
- Streak
- Gray white
- Luster
- Pearly to vitreous on cleavage surface, may be submetallic
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Fibrous, foliated, platy
- Cleavage
- Perfect on {001}, imperfect on {010}
- Rarity
- Common
- Uses
- Collector
- Host rock
- In banded iron formations and enclosing slates and schists
Where rockhounds find stilpnomelane
2 mapped spotsClassic worldwide localities
- Sterling mine, Antwerp, Jefferson Co., New York, USA
- Franklin, Sussex Co., New Jersey, USA
- Laytonville quarry, Mendocino Co., and a number of other places, California, USA
- Bald Knob, near Sparta, Alleghany Co., North Carolina, USA
- Obergrund, near Zuckmantel, Silesia, Poland
- Beroun na Moravě, Czech Republic
Field-hunting tip
Where it forms: In banded iron formations and enclosing slates and schists. If you start seeing quartz, siderite, apatite in float, you are in the right ground. Typical habit: fibrous, foliated, platy. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Jersey, Washington. Start trip planning there.
Common questions
How do you identify stilpnomelane?+
Where is stilpnomelane found?+
Can I find stilpnomelane in the United States?+
What rocks look like stilpnomelane?+
What minerals are found with stilpnomelane?+
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Find stilpnomelane on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
