Marcasite
Chemical Formula	FeS2
Species	Sulfides
Crystal System	Orthorhombic
Mohs Scale	6
Specific Gravity	4.875-4.887
Color	Tin-white on fresh surface, pale bronze-yellow, darkening on exposure, iridescent tarnish
Streak	Dark-grey to black.
Luster	Metallic
Diaphaneity	Opaque
Cleavage	Distinct/GoodDistinct on . in traces.
Fracture	Irregular/Uneven
Crystal Habit：Crystals typically tabular on {010}, curved faces common; stalactitic,reniform, massive; cockscomb and spearhead shapes due to twinning on .
Geological Setting：Most frequently found in sedimentary rocks and coal beds, as a replacement mineral forming fossils, it is a mineral of low-temperature, near-surface, environments, forming from acid solutions. Pyrite, the more stable form of FeS^2, forms under conditions of higher temperatures and lower acidity or alkaline environments.