Lennilenapeite is a rare phyllosilicate mineral typically found in the famous metamorphosed ore deposits of Franklin and Sterling Hill, New Jersey. It appears as brown to greenish-brown micaceous flakes or platy masses that are visually similar to stilpnomelane but distinguishable by its specific chemical composition and crystallography.
Is this lennilenapeite?
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 lennilenapeite with a known reference. Lennilenapeite 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. Lennilenapeite leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Lennilenapeite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: brown, greenish-brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy or micaceous aggregates.
Often confused with
Lennilenapeite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Lennilenapeite leaves yellowish-brown, Stilpnomelane leaves yellowish-brown to greenish-black.
How to tell apart: Streak differs — Lennilenapeite leaves yellowish-brown, Biotite leaves white.
How to tell apart: Streak differs — Lennilenapeite leaves yellowish-brown, Phlogopite leaves white.
Often found alongside lennilenapeite
Minerals reported to co-occur with lennilenapeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₆(Fe²⁺,Mg,Fe³⁺)₂₄(Si,Al)₃₄O₈₀(OH)₂₈·nH₂O
- Mohs hardness
- 3-4
- Density
- 2.81 g/cm³
- Colors
- Streak
- Yellowish-brown
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Platy or Micaceous Aggregates
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Metamorphosed Zinc Ore Deposits
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find lennilenapeite
Classic worldwide localities
- Franklin Mining District (New Jersey, USA)
- Sterling Hill (New Jersey, USA)
Field-hunting tip
Look in metamorphosed zinc ore deposits country — that is the host setting where lennilenapeite typically forms. If you start seeing willemite, franklinite, zincite in float, you are in the right ground. Field specimens usually show a platy or micaceous aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find lennilenapeite on the map
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