Schwertmannite
Iron-oxy-hydroxy-sulfate
From Wikipedia, the free encyclopedia
Schwertmannite is an iron-oxyhydroxysulfate mineral with an ideal chemical formula of Fe8O8(OH)6(SO4) · n H2O or Fe3+
16O
16(OH,SO
4)
12–13·10–12 H
2O.[2] 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.[3]
| Schwertmannite | |
|---|---|
| |
| General | |
| Category | Sulfate minerals |
| Formula | Fe8O8(OH)6(SO4) · n H2O |
| IMA symbol | Swm[1] |
| Strunz classification | 7.DE.15 |
| Crystal system | Tetragonal Dipyramidal class |
| Space group | Tetragonal H-M symbol: (4/m) Space group: P4/m |
| Identification | |
| Color | brownish yellow |
| Luster | earthy |
| Streak | yellow |
| Diaphaneity | opaque |
| References | [2][3] |
It was first described for an occurrence in Finland in 1994 and named for Udo Schwertmann (born 1927), a soil scientist at the Technical University of Munich, Munich, Germany.[4]
Schwertmannite (with a distinct "pin cushion" morphology) commonly forms in iron-rich, acidic 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.[5] However, it is more commonly reported as an orange precipitate in streams and lakes affected by acid mine drainage.[6] Schwertmannite is also known to be central to iron-sulfur geochemistry in acid sulfate soils associated with coastal lowlands.[7]