Schwertmannite is an iron-oxyhydroxysulfate

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

with an ideal chemical formula of or . It is an opaque

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the Cube (geometry), cube becomes a rectangular Pri ...

mineral typically occurring as brownish yellow encrustations. It has a

Mohs hardness The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fair ...

of 2.5 – 3.5 and a

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of 3.77 – 3.99. It was first described for an occurrence in

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

in 1994 and named for Udo Schwertmann (born 1927), a

soil scientist Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation t ...

at the

Technical University of Munich The Technical University of Munich (TUM or TU Munich; ) is a public research university in Munich, Bavaria, Germany. It specializes in engineering, technology, medicine, and applied and natural sciences. Established in 1868 by King Ludwig II ...

Munich, Germany Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...

. 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. However, it is more commonly reported as an orange precipitate in streams and lakes affected by

acid mine drainage Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines and coal mines. Acid rock drainage occurs naturally within some environments as part of the rock weatherin ...

. Schwertmannite is also known to be central to iron-sulfur geochemistry in acid sulfate soils associated with

coast A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

al lowlands.Burton, E.D., Bush, R.T., Sullivan, L.A. (2007). Reductive transformation of iron and sulfur in schwertmannite-rich accumulations associated with acidified coastal lowlands. ''Geochimica et Cosmochimica Acta'' 71, 4456–4473.

References

Iron(III) minerals Oxide minerals Sulfate minerals {{Sulfate-mineral-stub

See also

References