Minnesotaite is an iron silicate mineral with formula: (Fe2+,Mg)3Si4O10(OH)2.

[3] Minnesotaite was first described in 1944 for occurrences in the banded iron formations of northern Minnesota for which it was named.

Co-type localities are in the Cuyuna North Range, Crow Wing County and the Mesabi Range in St. Louis County.

[3][5] It occurs associated with quartz, siderite, stilpnomelane, greenalite and magnetite.

[2][6] In addition to the low grade metamorphic banded iron formations it has also been reported as an alteration mineral associated with sulfide bearing veins.