page_title: Marcasite
hierarchical_section_title: Marcasite
caption_attribution_description: English: Marcasite from chalk Locality&#160;: Cap Blanc Nez France. Size :8x6cm Français&#160;: Marcassite sur craie Cénomanienne. Macles de la sperkise. Localité: Cap Blanc-Nez France. Taille :8x6cm
context_page_description: The mineral marcasite, sometimes called “white iron pyrite”, is iron sulfide with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures do have in common that they contain the disulfide S₂²⁻ ion having a short bonding distance between the sulfur atoms. The structures differ in how these di-anions are arranged around the Fe²⁺ cations. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.
  On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. The thin, flat, tabular crystals, when joined in groups, are called “cockscombs”.
  Jewelers’ meaning
  In marcasite jewellery, pyrite used as a gemstone is called “marcasite” – that is, marcasite jewellery is made from pyrite, not from the mineral marcasite. Marcasite in the scientific sense is not used as a gem due to its brittleness.
context_section_description: The mineral marcasite, sometimes called “white iron pyrite”, is iron sulfide (FeS₂) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures do have in common that they contain the disulfide S₂²⁻ ion having a short bonding distance between the sulfur atoms. The structures differ in how these di-anions are arranged around the Fe²⁺ cations. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.
  On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. The thin, flat, tabular crystals, when joined in groups, are called “cockscombs”.
  Jewelers’ meaning
  In marcasite jewellery, pyrite used as a gemstone is called “marcasite” – that is, marcasite jewellery is made from pyrite, not from the mineral marcasite. Marcasite in the scientific sense is not used as a gem due to its brittleness. In the late medieval and early modern eras the word “marcasite” meant all iron sulfides in general, including both pyrite and the mineral marcasite. The narrower, modern scientific definition for marcasite as orthorhombic iron sulfide dates from 1845. The jewelers’ sense for the word “marcasite” pre-dates this 1845 scientific redefinition.
caption: Marcasite with tarnish (8×6 cm)
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