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, so 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, so 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, 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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