Arsenoclasite is an extremely rare manganese arsenate mineral known primarily from the Langban mines in Sweden. It typically appears as dark red, bladed crystals associated with manganese oxides in metamorphic iron deposits.
Is this arsenoclasite?
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 arsenoclasite with a known reference. Arsenoclasite sits at Mohs 5-6, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: orange brown, red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: bladed to granular aggregates.
Often confused with
Arsenoclasite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside arsenoclasite
Minerals reported to co-occur with arsenoclasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₅(AsO₄)₂(OH)₄
- Mohs hardness
- 5-6
- Density
- 4.16 g/cm³
- Colors
- Streak
- Yellowish brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Bladed to granular aggregates
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare fissure mineral in a metamorphosed Fe–Mn orebody (Långban, Sweden); in a sedimentary Fe–Mn deposit (Iron Monarch quarry, Australia)
Where rockhounds find arsenoclasite
Classic worldwide localities
- Långban, Värmland, Sweden
- Iron Monarch quarry, Iron Knob, South Australia
Field-hunting tip
Where it forms: A rare fissure mineral in a metamorphosed Fe–Mn orebody (Långban, Sweden); in a sedimentary Fe–Mn deposit (Iron Monarch quarry, Australia). If you start seeing sarkinite, adelite, allactite in float, you are in the right ground. Typical habit: bladed to granular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify arsenoclasite?+
Where is arsenoclasite found?+
Is arsenoclasite safe to handle?+
What rocks look like arsenoclasite?+
What minerals are found with arsenoclasite?+
What kind of rock does arsenoclasite form in?+
What is arsenoclasite used for?+
Find arsenoclasite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
