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, so Lennilenapeite leaves yellowish-brown, Stilpnomelane leaves yellowish-brown to greenish-black.
How to tell apart: Streak differs, so Lennilenapeite leaves yellowish-brown, Biotite leaves white.
How to tell apart: Streak differs, so 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, 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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