Akaganeite is a tunnel-structured iron oxyhydroxide that frequently forms in chloride-rich environments. It typically appears as brownish, needle-like acicular crystal clusters or earthy crusts and is often found as a weathering product in iron deposits.
Is this akaganeite?
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 akaganeite with a known reference. Akaganeite 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. Akaganeite leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Akaganeite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: reddish-brown, brown, yellowish-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular or fibrous aggregates, coatings, and crusts.
Often confused with
Akaganeite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Iron Ore is the harder of the two (Mohs 5-6.5 vs. 3-4); streak differs — Akaganeite leaves yellowish-brown, Iron Ore leaves reddish-brown to black; luster reads dull on Akaganeite and metallic to submetallic on Iron Ore.
How to tell apart: Lepidocrocite is the harder of the two (Mohs 5 vs. 3-4); streak differs — Akaganeite leaves yellowish-brown, Lepidocrocite leaves orange-red; luster reads dull on Akaganeite and submetallic on Lepidocrocite.
Often found alongside akaganeite
Minerals reported to co-occur with akaganeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeO(OH,Cl)
- Mohs hardness
- 3-4
- Density
- 3.5 g/cm³
- Streak
- Yellowish-brown
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or Fibrous Aggregates, Coatings, And Crusts
- Cleavage
- Distinct On {110}
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Hydrothermal Veins, Gossans, And Altered Iron-rich Deposits
- Typical price
- $20-100 per specimen
Where rockhounds find akaganeite
Classic worldwide localities
- Chihuahua, Mexico
- Katanga, DR Congo
- Harz Mountains, Germany
- Cumberland, England
Field-hunting tip
Look in hydrothermal veins, gossans, and altered iron-rich deposits country — that is the host setting where akaganeite typically forms. If you start seeing goethite, hematite, quartz in float, you are in the right ground. Field specimens usually show a acicular or fibrous aggregates, coatings, and crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find akaganeite on the map
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