minnesotaite

{{infobox mineral | name = Minnesotaite | boxwidth = | boxbgcolor = | image = Minnesotaite.jpg | imagesize = | alt = | caption = Minnesotaite | category = Phyllosilicate minerals | group = Pyrophyllite-Talc group | formula = (Fe2+,Mg)3Si4O10(OH)2 | IMAsymbol = Mns | molweight = | strunz = 9.EC.05 | dana = | system = Triclinic | class = Pinacoidal () (same H-M symbol) | symmetry = P | unit cell = a = 5.623(2) Å, b = 9.419(2) Å, c = 9.624(3) Å; α = 85.21(3)°, β = 95.64(3)°, γ = 90.00°; Z = 2 | color = Greenish gray to olive-green | colour = | habit = Occurs as microscopic needles or platelets, the needles occur in radiating clusters or in sheaves; also fibrous | twinning = Inferred based on X-ray patterns | cleavage = Perfect on {001}, micaceous | fracture = Uneven and irregular | tenacity = Brittle | mohs = 1.5 - 2 | luster = Greasy to waxy, dull | streak = | diaphaneity = Translucent | gravity = 3.01 | density = | polish = | opticalprop = Biaxial (-) | refractive = nα = 1.578 - 1.583 nβ = 1.578 - 1.622 nγ = 1.615 - 1.623 | birefringence = δ = 0.037 - 0.040 | pleochroism = X= pale green, Z= colorless to pale greenish yellow | 2V = Measured: 4° | dispersion = r 2+,Mg)3Si4O10(OH)2. It crystallizes in the triclinic crystal system and occurs as fine needles and platelets with other silicates. It is isostructural with the pyrophyllite-talc mineral group.

==Occurrence== 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.