Schwertmannite
A variety of Minerals
What is Schwertmannite?
Schwertmannite is an iron-oxyhydroxysulfate mineral with an ideal chemical formula of Fe8O8(OH)6(SO4)·nH2O or Fe16O16(OH,SO4)12-13·10-12H2O. It is an opaque tetragonal mineral typically occurring as brownish yellow encrustations. It has a Mohs hardness of 2.5 - 3.5 and a specific gravity of 3.77 - 3.99. It was first described for an occurrence in Finland in 1994 and named for Udo Schwertmann (born 1927) soil scientist, Technical University of Munich, Munich, Germany. Schwertmannite (with a distinct "pin cushion" morphology) commonly forms in iron-rich, acid sulfate waters in the pH-range of 2 - 4. The mineral was first recognised officially as a new mineral from a natural acid-sulfate spring occurrence at Pyhäsalmi, Finland. However, it is more commonly reported as an orange precipitate in streams and lakes affected by acid mine drainage. Schwertmannite is also known to be central to iron-sulfur geochemistry in acid sulfate soils associated with coastal lowlands.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Schwertmannite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Schwertmannite Localities Map
See where Schwertmannite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- brownish yellow
- Hardness (Mohs)
- 1 - 2
- Streak
- yellow
Chemical Properties
- Chemical Formula
- Fe3+16(OH,SO4)12-13O16 · 10-12H2O
- Elements
- Fe, H, O, S
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Schwertmannite FAQs
How do I identify Schwertmannite?
Schwertmannite can be identified by its hardness of 1 - 2 on the Mohs scale, brownish yellow color. Look for these key characteristics when examining specimens.
What color is Schwertmannite?
Schwertmannite typically appears in brownish yellow. Color can vary depending on impurities and formation conditions.
How hard is Schwertmannite?
Schwertmannite has a hardness of 1 - 2 on the Mohs scale. This makes it a soft mineral that can be scratched easily.
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