Schwertmannite is an iron oxyhydroxysulfate mineral typically formed in acidic, sulfate-rich waters associated with mine drainage. It usually appears as fine-grained, yellow-brown coatings or crusts and is identified by its distinctive morphology in iron-rich oxidizing environments.
Is this schwertmannite?
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 schwertmannite with a known reference. Schwertmannite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Schwertmannite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Schwertmannite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, orange.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: acicular, fibrous, globular, crusts.
Often confused with
Schwertmannite 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. 2-3); streak differs — Schwertmannite leaves yellow, Iron Ore leaves reddish-brown to black; luster reads dull on Schwertmannite and metallic to submetallic on Iron Ore.
How to tell apart: Lepidocrocite is the harder of the two (Mohs 5 vs. 2-3); streak differs — Schwertmannite leaves yellow, Lepidocrocite leaves orange-red; luster reads dull on Schwertmannite and submetallic on Lepidocrocite.
How to tell apart: Luster reads dull on Schwertmannite and vitreous on Jarosite.
Often found alongside schwertmannite
Minerals reported to co-occur with schwertmannite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₈O₈(OH)₆(SO₄)·nH₂O
- Mohs hardness
- 2-3
- Density
- 3.8 g/cm³
- Streak
- Yellow
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Acicular, Fibrous, Globular, Crusts
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Scientific Research
- Host rock
- Acid Mine Drainage Environments, Stream Sediments, And Sulfide Mine Tailings.
- Typical price
- $10-50 per specimen
Where rockhounds find schwertmannite
Classic worldwide localities
- Pyhäsalmi mine, Finland
- Rio Tinto, Spain
- Iron Mountain, California, USA
- Wheal Jane, Cornwall, UK
Field-hunting tip
Look in acid mine drainage environments, stream sediments, and sulfide mine tailings. country — that is the host setting where schwertmannite typically forms. If you start seeing goethite, jarosite, ferrihydrite in float, you are in the right ground. Field specimens usually show a acicular, fibrous, globular, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find schwertmannite on the map
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