Finnemanite is a rare lead arsenite chloride mineral found almost exclusively in the historic Langban mines of Sweden. It is highly sought after by collectors for its brilliant adamantine luster and well-defined, hexagonal prismatic crystal habits.
Is this finnemanite?
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 finnemanite with a known reference. Finnemanite sits at Mohs 2.5, 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: subadamantine.
- 4Match the color rangeCompare against the expected color range: gray, black.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals, often with pyramidal terminations.
Often confused with
Finnemanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Mimetite is the harder of the two (Mohs 3.5-4 vs. 2.5); luster reads subadamantine on Finnemanite and resinous to subadamantine on Mimetite.
How to tell apart: Pyromorphite is the harder of the two (Mohs 3.5-4 vs. 2.5); luster reads subadamantine on Finnemanite and resinous to subadamantine on Pyromorphite.
Often found alongside finnemanite
Minerals reported to co-occur with finnemanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₅(AsO₃)₃Cl
- Mohs hardness
- 2.5
- Density
- 7.265 g/cm³
- Streak
- White
- Luster
- Subadamantine
- Transparency
- Translucent to opaque
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic crystals, often with pyramidal terminations
- Cleavage
- {1011}, distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In crevices in hematite in a metamorphosed Fe–Mn orebody (Långban, Sweden)
Where rockhounds find finnemanite
Classic worldwide localities
- Långban, Värmland, Sweden
- Puttapa zinc mine, near Beltana, South Australia
Field-hunting tip
Where it forms: In crevices in hematite in a metamorphosed Fe–Mn orebody (Långban, Sweden). If you start seeing hematite, rouseite, trigonite in float, you are in the right ground. Typical habit: prismatic crystals, often with pyramidal terminations. Train your eye for that shape before scanning the outcrop.
Common questions
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Find finnemanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
