Hardness: 6 to 6.5
Marcasite, sometimes called white iron pyrite, is iron sulfide (FeS2). Marcasite is a secondary mineral--it forms by chemical alteration of a primary mineral such as chalcopyrite. 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."
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 all of the coal mines in southeastern Kansas.
The sample pictured above is from Gove County, Kansas
Buchanan, Rex C., Tolsted, Laura L., and Swineford, Ada, 1986, Kansas Rocks and Minerals: Kansas Geological Survey, Educational Series 2, 60 p.
Klein, Cornelis, 1993, Manual of Mineralogy (after James D. Dana), 21st Edition: New York, Wiley, 681 p.
Unless noted otherwise, illustrations by Jennifer Sims, Kansas Geological Survey; photographs by John Charlton, Kansas Geological Survey; text by Liz Brosius, Kansas Geological Survey.
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