Mineral · Calcite group
Siderite
FeCO3
Siderite is iron carbonate, found as brown curved rhombs on quartz and fluorite from Cornwall, Panasqueira (Portugal) and Bolivia, and as the ironstone concretions that enclose Mazon Creek fossils. Brown lenticular crystals with a pearly lustre and a slight magnetism after heating identify it. Siderite oxidises to goethite on weathering.
| Formula | FeCO3 |
|---|---|
| IMA status | grandfathered |
| Crystal system | Trigonal |
| Mohs hardness | 3.5–4.5 |
| Group | Calcite group |
| Type locality | None |
| Streak | White to pale yellow |
| Specific gravity | 3.96 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Elsewhere
Cite this article
Stratum Strata. "Siderite" (Mineral). Stratum Strata pack 2026.09, as of 2026-09-21. https://stratum.black/strata/minerals/siderite. Accessed 2026-09-21.
@misc{stratum-siderite,
title = {Siderite},
author = {{Stratum Strata}},
howpublished = {\url{https://stratum.black/strata/minerals/siderite}},
year = {2026},
note = {Mineral article, Stratum Strata pack 2026.09, as of 2026-09-21; sources: stratum, wikidata, commons. Accessed 2026-09-21.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.