Where is Calcite with Marcasite found?
Calcite (CaCO3) and Marcasite (FeS2)
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Open the appCalcite with Marcasite occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Calcite with Marcasite
Illinois, USA
Known for concretions of marcasite and calcite, particularly in coal-bearing strata.
Missouri, USA
Various lead-zinc districts, where calcite and marcasite can be found in hydrothermal veins.
Oklahoma, USA
Certain sedimentary formations contain calcite and marcasite associations.
Germany
Historical mining districts, particularly in areas with sedimentary iron sulfide deposits.
United Kingdom
Certain localities, especially in areas with coal measures or Jurassic sedimentary rocks.
Collecting tips
- Look in Sedimentary Environments. Focus on areas with shales, limestones, and coal seams, as these are common hosts for both minerals.
- Check Concretions and Geodes. Marcasite often forms within concretions, which may also contain calcite linings or crystals.
- Examine Hydrothermal Veins. In some low-temperature hydrothermal settings, calcite and marcasite can co-precipitate.
- Beware of 'Pyrite Disease'. Marcasite is prone to decomposition. Collect specimens that appear stable and store them in a dry, sealed environment to prevent degradation.
- Acid Test for Calcite. Calcite will effervesce vigorously with dilute hydrochloric acid, a useful test to confirm its presence.
Quick Check
- Color:
- Calcite: White/colorless; Marcasite: Pale bronze-yellow/off-white
- Luster:
- Calcite: Vitreous; Marcasite: Metallic
- Streak:
- Calcite: White; Marcasite: Greenish-black to brownish-black
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