Marcasite, sometimes called white iron pyrite, is a secondary mineral because it forms by chemical alteration of a primary mineral, such as chalcopyrite. It is a brittle material with thin, flat, tabular crystals that may be joined in groups called "cockscombs." Rose-shaped clusters are called marcasite rosettes.
In Kansas, marcasite occurs as concretions and crystals in coal, shale, and limestone. Well-developed crystals have been taken from the lead and zinc mines of the Tri-State district in Cherokee County and can be found in southeast Kansas coal mines.
Chemical compound: iron sulfide
Chemical formula: FeS2 (Fe = iron, S = sulfur)
Color: pale yellow to near white on fresh surface; tarnishes to dark yellow or brown
Specific gravity: 4.8
Amount of transparency: opaque
Buchanan, R., 2010, Kansas Geology: An Introduction to Landscapes, Rocks, Minerals, and Fossils (2nd ed.): Lawrence, Kansas, University Press of Kansas, 240 p.
Buchanan, R., and McCauley, J. R., 2010, Roadside Kansas: A Traveler's Guide to Its Geology and Landmarks (2nd ed.): Lawrence, Kansas, University Press of Kansas, 392 p.
Kansas Rocks and Minerals, Kansas Geological Survey Educational Series 2