Larsenite is an extremely rare lead-zinc silicate known almost exclusively from the famous Franklin and Sterling Hill mines in New Jersey. It is most easily identified by its brilliant yellow fluorescence under shortwave ultraviolet light. Collectors should look for it in association with other characteristic fluorescent minerals from the Franklin mining district.
Is this larsenite?
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 larsenite with a known reference. Larsenite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine, pearly on platy surfaces.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, striated.
Often confused with
Larsenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Willemite is the harder of the two (Mohs 5.5 vs. 3); luster reads adamantine, pearly on platy surfaces on Larsenite and vitreous to resinous on Willemite.
How to tell apart: Luster reads adamantine, pearly on platy surfaces on Larsenite and vitreous on Hardystonite.
Often found alongside larsenite
Minerals reported to co-occur with larsenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbZnSiO₄
- Mohs hardness
- 3
- Density
- 5.90 g/cm³
- Colors
- Streak
- White
- Luster
- Adamantine, pearly on platy surfaces
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, striated
- Cleavage
- {120}, distinct
- Fluorescence
- Bright yellow under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare secondary mineral in veins cutting and replacing coarse, massive willemite-franklinite ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA)
Where rockhounds find larsenite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
- Tsumeb, Namibia
- Puttapa zinc mine, near Beltana, South Australia
Field-hunting tip
Where it forms: A very rare secondary mineral in veins cutting and replacing coarse, massive willemite-franklinite ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA). If you start seeing willemite, clinohedrite, esperite in float, you are in the right ground. Typical habit: acicular, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify larsenite?+
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Is larsenite safe to handle?+
What rocks look like larsenite?+
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Find larsenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
