Madocite is a mineral with a chemical formula of . Madocite was named for the locality of discovery,

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. It is found in the marbles of the Precambrian Grenville Limestone. It is orthorhombic (rectangular prism with a rectangular base) and in the point group ''mm2''. Its crystals are elongated and striated along 01to a size of 1.5 mm. Madocite is anisotropic and classified as having high relief. It also displays strong pleochroism. Madocite is found in small clusters in marble pits (near Madoc, Ontario), and was originally categorized in the 1920s as an unidentified sulfosalt mineral in an assemblage of pyrite, sphalerite, and jamesonite in marble. Later research was done by John Leslie Jambor, John L. Jambor in the 1960s who went to the site and collected samples of the assemblages.History of discovery
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References

Antimony minerals Arsenic minerals Lead minerals Sulfosalt minerals Orthorhombic minerals {{sulfide-mineral-stub