Akrochordite is a rare manganese magnesium arsenate mineral typically found in metamorphosed manganese deposits. It usually forms as attractive brownish, radial, or granular aggregates and is highly sought after by mineral collectors for its unique crystal structures.
Is this akrochordite?
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 akrochordite with a known reference. Akrochordite sits at Mohs 3.5, 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: dull.
- 4Match the color rangeCompare against the expected color range: reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: radial aggregates, granular, crusts.
Often confused with
Akrochordite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads dull on Akrochordite and vitreous on Brandtite.
How to tell apart: Synadelphite is the harder of the two (Mohs 4.5 vs. 3.5); streak differs, so Akrochordite leaves white, Synadelphite leaves yellowish-brown; luster reads dull on Akrochordite and vitreous, adamantine to submetallic on Synadelphite.
Often found alongside akrochordite
Minerals reported to co-occur with akrochordite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MnMn₂Mn₂(AsO₄)₂(OH)₄(H₂O)₄
- Mohs hardness
- 3.5
- Density
- 3.19-3.35 g/cm³
- Colors
- Streak
- White
- Luster
- Dull
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Radial aggregates, granular, crusts
- Cleavage
- On {010}, perfect; a second, perpendicular to the first
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare mineral in hausmannite ore from a metamorphosed Fe–Mn orebody (Långban, Sweden); in a metamorphosed stratiform zinc orebody (Sterling Hill, New Jersey, USA)
Where rockhounds find akrochordite
Classic worldwide localities
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Långban, Värmland, Sweden
Field-hunting tip
Where it forms: A rare mineral in hausmannite ore from a metamorphosed Fe–Mn orebody (Långban, Sweden); in a metamorphosed stratiform zinc orebody (Sterling Hill, New Jersey, USA). If you start seeing pyrochroite, barite, hausmannite in float, you are in the right ground. Typical habit: radial aggregates, granular, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find akrochordite on the map
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