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, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to resinous.
- 4Match the color rangeCompare against the expected color range: brownish black, green, light green, dark brown.
- 5Look at form & habitCrystal system: triclinic. Typical habit: aggregates, platy.
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 brown, Stilpnomelane leaves gray white; luster reads vitreous to resinous on Lennilenapeite and pearly to vitreous on cleavage surface, may be submetallic on Stilpnomelane.
How to tell apart: Streak differs, so Lennilenapeite leaves brown, Biotite leaves white; luster reads vitreous to resinous on Lennilenapeite and splendent to submetallic, vitreous, pearly on cleavage on Biotite.
How to tell apart: Streak differs, so Lennilenapeite leaves brown, Phlogopite leaves white; luster reads vitreous to resinous on Lennilenapeite and pearly to submetallic on cleavage on Phlogopite.
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
- K₄Mn₄₈[Si₆₄Al₈]O₁₆₄(OH)₅₂·nH₂O
- Mohs hardness
- ~3
- Density
- 2.72 g/cm³
- Streak
- Brown
- Luster
- Vitreous to resinous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Aggregates, platy
- Cleavage
- Perfect on {001}, imperfect on fhk0g
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Apparently as both a primary and a late-stage low-temperature hydrothermal mineral in a metamorphosed stratiform zinc deposit
Where rockhounds find lennilenapeite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
Field-hunting tip
Where it forms: Apparently as both a primary and a late-stage low-temperature hydrothermal mineral in a metamorphosed stratiform zinc deposit. If you start seeing nelenite, tirodite, franklinite in float, you are in the right ground. Typical habit: aggregates, platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify lennilenapeite?+
Where is lennilenapeite found?+
What rocks look like lennilenapeite?+
What minerals are found with lennilenapeite?+
What kind of rock does lennilenapeite form in?+
What is lennilenapeite used for?+
Find lennilenapeite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
