• Specimen Number

  24

• Description

  Irregular boulder of complex rock that is likely a coarse igneous protolith with phenocrysts and pervasive hydrothermal alteration. Identified by staff from the State Geological Survey. Malachite stain on rim suggests bulk rock is metalliferous. It's possible the metal crystals were visible when the sample was collected, but have since oxidized.

• Classification

  Complex. Hydrothermally altered protolith.  Ore. Silver.

• Location & Occurrence

  Malachite and rust indicate likely ore from silver mines in southwestern state near Phillipsberg, confirming the Hartford Courant identification as "silver-bearing ore." The Connecticut Campus identified it as having come from Iowa.

• Geologic Age

  Likely of Mesozoic age (synorogenic). Protolith and alteration have different ages.

• Geoheritage

  Sample of Cordilleran ore illuminates the story of western mining.

• Links

  Link to State Geological Map from USGS.  Link to Montana Bureau of Mines & Geology.

• Other

  Mentioned as "silver-bearing ore" in Hartford Courant 1937, confirming informants speculation of location.

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