State by State
- Specimen Number
Cut block of pink granite or granite gneiss showing layering of milky, mafic-poor bands to lower left and more granular, but weakly foliated masses to right. Identified by survey staff from Western Michigan University as a granite or granitic gneiss.
Igneous. Plutonic. Granitic. Granite gneiss.
- Location & Occurrence
Identified by state survey staff at Western Michigan University as likely from Dickinson County, Upper Peninsula of Michigan, near the city and former mines of Iron Mountain.
- Geological Age
PreCambrian, unknown. Later Archaean or Early Proterozoic.
Arguably the oldest rock in the collection from and ancient craton of North America, the nucleus for the Appalachians and Cordillera. The Upper Michigan Peninsula was, in the early 19th century, the wild northwest territory of the United States. Mineral exploration was key to our early industrial success.