Latitude & Longitude (WGS84):	46° 44' 20'' North , 89° 7' 52'' West
Latitude & Longitude (decimal):	46.73889,-89.13111
GeoHash:	G#: f029gu89y
Locality type:	Mine
Köppen climate type:	Dfb : Warm-summer humid continental climate
Nearest Settlements:	Place Population Distance Ontonagon 1,324 (2017) 20.2km White Pine 474 (2017) 34.5km

Commodities (Major) - Copper; (Minor) - Silver
Deposit Type: Secondary Enrichment
Development Status: Past Producer
Host Rock Unit: Portage Lake Volcanics
Host Rock: Basalt

An underground copper mine consisting of three shafts located near Mass City. The Flintsteel River Mining Company was organized in 1855 when land was set off from the Minesota Mine that contained a vein of copper that, according to Minesota Mine reports, was not productive. Before the land was set off, the Minesota was sinking two shafts on the property in 1852; however, one had to be closed off due to the persistent problem of water in the shaft. Several masses of copper were removed, including one weighing 10 tons. In 1864, the mine produced almost 30,000 pounds of copper. By 1865, the mine had been operating successfully for several years with three operating shafts and produced a little over 211,000 pounds of copper. Work continued until 1871 when the company reorganized as the Flintsteel Copper Company, and in the process merged with the nearby Caledonia Mining Company. Between 1871 and 1881 when the mine went idle, it produced 466,000 pounds of copper. Today, the mine piles are great for copper, silver, and the occasional datolite.

Regions containing this locality

North America Plate	Tectonic Plate
Keweenaw Peninsula, Michigan, USA	Peninsula

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Stenian 1000 - 1200 Ma ID: 2928167

Portage Lake Volcanics Age: Stenian (1000 - 1200 Ma) Stratigraphic Name: Portage Lake Volcanics Description: Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks. Comments: This unit is the same as unit Yp on paper map of Sims (1992). Description is taken from that unit description. Original map source: Cannon, W.F., Kress, T.H., Sutphin, D.M., Morey, G.B., Meints, Joyce, and Barber-Delach, Robert, 1997, Digital Geologic Map and mineral deposits of the Lake Superior Region, Minnesota, Wisconsin, Michigan: USGS Open-File Report 97-455 (version 3, Nov. 19 Lithology: Major:{basalt}, Minor:{basaltic andesite}, Incidental:{rhyolite, sandstone mudstone} Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Mesoproterozoic 1000 - 1600 Ma ID: 3190266

Mesoproterozoic volcanic rocks Age: Mesoproterozoic (1000 - 1600 Ma) Comments: Mid-Continent Rift Lithology: Bimodal volcanic rocks Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References