The Cuyuna range, located in east-central Minnesota, consists of a
sequence of argillite, siltstone, iron-formation, graywacke, slate, and
quartzite of early Proterozoic age. Manganese-bearing materials occur
within the iron-rich strata of the Trommald Formation and the Rabbit Lake
Formation. Computer-assisted resource estimates, based on exploration
drill hole information, indicate that the Cuyuna range contains a minimum
of 176 million metric tons (MMT) of marginally economic manganiferous rock
with an average grade of 10.46 weight percent manganese. The calculated
18.5 MMT of manganese on the Cuyuna range could supply this country's
needs for this important and strategic metal for nearly 14 years. An
additional resource of 6.9 MMT of manganese metal is available in the
lower grade deposits. The vast majority of these calculated resources are
extractable by current surface mining techniques.
Beltrame, R.J.; Holtzman, Richard C.; Wahl, Timothy E..
RI-24 Manganese Resources of the Cuyuna Range, East-Central Minnesota.
Minnesota Geological Survey.
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