Feroxyhyte is a rare iron oxyhydroxide polymorph that typically forms as an unstable, fine-grained precipitate in marine environments or oxidation zones. It is rarely found as well-developed crystals, appearing instead as thin coatings, nodules, or earthy masses. Collectors prize it primarily for its occurrence in ferromanganese nodules from deep-sea settings.
Is this feroxyhyte?
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 feroxyhyte with a known reference. Feroxyhyte sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Feroxyhyte leaves a brown streak.
- 3Read the lusterHold the specimen under a strong light. Feroxyhyte typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: red-brown, brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: fine-grained, massive, aggregates.
Often confused with
Feroxyhyte 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. 2); streak differs — Feroxyhyte leaves brown, Iron Ore leaves reddish-brown to black; luster reads dull on Feroxyhyte and metallic to submetallic on Iron Ore.
How to tell apart: Lepidocrocite is the harder of the two (Mohs 5 vs. 2); streak differs — Feroxyhyte leaves brown, Lepidocrocite leaves orange-red; luster reads dull on Feroxyhyte and submetallic on Lepidocrocite.
Often found alongside feroxyhyte
Minerals reported to co-occur with feroxyhyte. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeO(OH)
- Mohs hardness
- 2
- Density
- 4.15 g/cm³
- Streak
- Brown
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Fine-grained, Massive, Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Marine Sediments, Ferromanganese Nodules, Oxidation Zones
- Typical price
- $20-100 per specimen
Where rockhounds find feroxyhyte
Classic worldwide localities
- Germany
- Russia
- USA
Field-hunting tip
Look in marine sediments, ferromanganese nodules, oxidation zones country — that is the host setting where feroxyhyte typically forms. If you start seeing goethite, lepidocrocite, hematite in float, you are in the right ground. Field specimens usually show a fine-grained, massive, aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find feroxyhyte on the map
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