Minnesotaite

---

title: "Minnesotaite" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["triclinic-minerals", "minerals-in-space-group-2", "pyrophyllite-talc-group"] description: "Phyllosilicate mineral in the pyrophyllite-talc group" topic_path: "general/triclinic-minerals" source: "https://en.wikipedia.org/wiki/Minnesotaite" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Phyllosilicate mineral in the pyrophyllite-talc group ::

::data[format=table title="infobox mineral"]

Field	Value
name	Minnesotaite
image	Minnesotaite.jpg
caption	Minnesotaite
category	Phyllosilicate minerals
group	Pyrophyllite-Talc group
formula	(Fe2+,Mg)3Si4O10(OH)2
IMAsymbol	Mns
strunz	9.EC.05
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
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
diaphaneity	Translucent
gravity	3.01
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
references
::

| 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 | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = Minnesotaite is an iron silicate mineral with formula: (Fe2+,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.

It occurs associated with quartz, siderite, stilpnomelane, greenalite and magnetite. In addition to the low grade metamorphic banded iron formations it has also been reported as an alteration mineral associated with sulfide bearing veins.

References

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. [http://rruff.geo.arizona.edu/doclib/hom/minnesotaite.pdf Handbook of Mineralogy]
3. [http://www.mindat.org/min-2722.html Minnesotaite on Mindat.org]
4. [http://www.webmineral.com/data/Minnesotaite.shtml Minnesotaite on Webmineral]
5. Gruner, John. (1946). "The Mineralogy and Geology of the Taconites and Iron Ores of the Mesabi Range, Minnesota". Office of the Commissioner of the Iron Range Resources and Rehabilitation.
6. [http://www.minsocam.org/ammin/AM29/AM29_363.pdf Gruner, John W., ''The Composition and Structure of Minnesotaite, a Common Iron Silicate in Iron Formations,'' American Mineralogist, 1944, 29, 363-372]

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