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, so 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, so 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, 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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