Arseniopleite is a rare manganese arsenate mineral found almost exclusively in the famous Långban mines of Sweden. Collectors prize it for its rich brownish-red hues and its association with other exotic manganese minerals found in regionally metamorphosed ore bodies.
Is this arseniopleite?
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 arseniopleite with a known reference. Arseniopleite 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. Streak: yellowish brown.
- 3Read the lusterHold the specimen under a strong light. Luster: dull.
- 4Match the color rangeCompare against the expected color range: cherry, reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive.
Often confused with
Arseniopleite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Arseniopleite leaves yellowish brown, Allactite leaves gray to faint brown; luster reads dull on Arseniopleite and vitreous, slightly greasy on fracture surfaces on Allactite.
How to tell apart: Braunite is the harder of the two (Mohs 6-6.5 vs. 3-4); streak differs, so Arseniopleite leaves yellowish brown, Braunite leaves brownish black to steel-gray; luster reads dull on Arseniopleite and submetallic on Braunite.
How to tell apart: Hausmannite is the harder of the two (Mohs 5.5 vs. 3-4); streak differs, so Arseniopleite leaves yellowish brown, Hausmannite leaves dark reddish brown; luster reads dull on Arseniopleite and submetallic on Hausmannite.
Often found alongside arseniopleite
Minerals reported to co-occur with arseniopleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCaMnMn₂(AsO₄)₃
- Mohs hardness
- 3-4
- Density
- 4.17-4.22 g/cm³
- Colors
- CherryReddish brown
- Streak
- Yellowish brown
- Luster
- Dull
- Transparency
- Opaque to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive
- Cleavage
- On pseudo-{10*1}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As fracture fillings and thin veins in banded dolostone (Sjö mine, Sweden); in a metamorphosed Fe-Mn orebody (Långban, Sweden)
Where rockhounds find arseniopleite
Classic worldwide localities
- Sjö mine, near Grythyttan, Örebro, and at Långban, Värmland, Sweden
Field-hunting tip
Where it forms: As fracture fillings and thin veins in banded dolostone (Sjö mine, Sweden); in a metamorphosed Fe-Mn orebody (Långban, Sweden). If you start seeing rhodonite, tephroite, hedyphane in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify arseniopleite?+
Where is arseniopleite found?+
Is arseniopleite safe to handle?+
What rocks look like arseniopleite?+
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Find arseniopleite on the map
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