Minerals

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General Information

Marcasite

Marcasite is related to pyrite because it has the same chemical formula and is therefore made of the same elements. Marcasite can become the subject of a process called "pyrite decay". This will transform the marcasite into a white powder. Because of a reaction with the moist from the air, sulphuric acid forms that causes the decay by desintegrating the other sulphuric bonds in the mineral. (See the photos below for the result of this. They are two different marcasite spheres.)[1]

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Chemical & Physical Information

Trivial NameMarcasite
Chemical NameIron Disulfide
Chemical FormulaFeS2
Density4.875 g·cm-3
Molar mass119.98 g·mol-1
Hardness6-6,5
Crytal systemOrthorombic
Unit cell?
Crystal habit?
FractureRough
CleavageUnclear [010]
ColourBronze yellow to tin white
LusterMetal
StreakGreen like to black grey
OpacityOpaque
SafetySafe
ExtraCan decay to a white powder.
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Photos

Marcasite

(3 cm)

Marcasite

(3 cm)

Marcasite

(3 cm)

Marcasite

(3 cm)

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Sources

[1] Wikipedia

[2] Specimen from my personal collection, photo taken by me.