Marcasite
Species
Common · FeS₂
The same iron disulfide as pyrite, built orthorhombic instead of cubic, paler and far less stable: specimens crumble to powder and sulfuric acid in damp air. The marcasite of jewellery is almost always pyrite.
Identity
- Formula
- FeS₂
- Chemical class
- Sulfide
- Also known as
- White iron pyrite
Crystallography
- Crystal system
- Orthorhombic
- Habits
- Tabular, Bladed, Nodular, Botryoidal
- Fracture
- Subconchoidal
Physical properties
- Mohs hardness
- 6
- Density
- 4.89 g/cm³
- Luster
- Metallic
- Colors
- bronze, light brass yellow, tin white
- Streak
- gray brownish black
- Transparency
- Opaque
Geology
- Origins
- Sedimentary, Hydrothermal
- Host rocks
- Limestone and chalk, Sandstone, shale and clay
- Associated minerals
- Pyrite, Galena, Sphalerite, Calcite
- Found in
- Coal seam
- Geography
- United Kingdom, France, USA
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- Marcasite. Mindat.org (Hudson Institute of Mineralogy).
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Marcasite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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