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. Arsenoclasite leaves a yellowish brown streak.
- 3Read the lusterHold the specimen under a strong light. Arsenoclasite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark red, brownish 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.
How to tell apart: Arsenoclasite is noticeably harder (Mohs 5-6 vs. 3-4); streak differs — Arsenoclasite leaves yellowish brown, Allactite leaves light brown.
How to tell apart: Streak differs — Arsenoclasite leaves yellowish brown, Flinkite leaves light brown.
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
- 4.24 g/cm³
- Colors
- Streak
- Yellowish Brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Bladed to Granular Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Manganiferous Iron Ore Deposits
- Typical price
- $50-300+ per specimen depending on size and quality
Where rockhounds find arsenoclasite
Classic worldwide localities
- Langban, Sweden
Field-hunting tip
Look in manganiferous iron ore deposits country — that is the host setting where arsenoclasite typically forms. If you start seeing hausmannite, jacobsite, calcite in float, you are in the right ground. Field specimens usually show a bladed to granular aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find arsenoclasite on the map
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