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. Stilpnomelane leaves a yellowish-brown to greenish-black streak.
- 3Read the lusterHold the specimen under a strong light. Stilpnomelane typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black, bronze, greenish-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, foliated masses, radiating sprays.
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 yellowish-brown to greenish-black, Biotite leaves white.
How to tell apart: Streak differs, so Stilpnomelane leaves yellowish-brown to greenish-black, Chlorite leaves white.
How to tell apart: Streak differs, so Stilpnomelane leaves yellowish-brown to greenish-black, Muscovite leaves white.
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
- K(Fe²⁺,Mg,Fe³⁺)₈(Si,Al)₁₂O₃₀(OH)₁₂·nH₂O
- Mohs hardness
- 3-4
- Density
- 2.7-3.0 g/cm³
- Streak
- Yellowish-brown to Greenish-black
- Luster
- Pearly
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Foliated Masses, Radiating Sprays
- Cleavage
- Perfect Basal
- Rarity
- Common
- Uses
- Collector
- Host rock
- Low to Medium Grade Metamorphic Rocks, Iron Formations
- Typical price
- $10-60 per specimen
Where rockhounds find stilpnomelane
1 mapped spotsClassic worldwide localities
- Czech Republic
- Canada
- Germany
- USA
- New Zealand
Field-hunting tip
Look in low to medium grade metamorphic rocks, iron formations country, the host setting where stilpnomelane typically forms. If you start seeing quartz, albite, magnetite in float, you are in the right ground. Field specimens usually show a platy crystals, foliated masses, radiating sprays habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Jersey. Start trip planning there.
Common questions
How do you identify stilpnomelane?+
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Find stilpnomelane on the map
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