Groutite is a

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

oxide mineral The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal alloys. The hydroxide-bearing minerals are typically included in the oxide class. Minerals with complex anion groups such as the sil ...

with formula Mn³⁺O(OH). It is a member of the

diaspore Diaspore ()also called diasporite, empholite, kayserite, or tanatariteis an aluminium hydroxide oxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but ...

group and is trimorphous with

manganite Manganite is a mineral composed of manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic). Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped togethe ...

and feitknechtite. It forms lustrous black crystals in the orthorhombic system. It occurs in weathered

banded iron formation Banded iron formations (BIFs; also called banded ironstone formations) are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert. They can be up to several hundred meters in thickness and e ...

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

manganese ore bodies and

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

ore environments. It was first described in 1945 for an occurrence in the Mahnomen mine,

Cuyuna Range The Cuyuna Range is an inactive iron range to the southwest of the Mesabi Range, largely within Crow Wing County, Minnesota. It lies along a line between Brainerd, Minnesota, and Aitkin, Minnesota. The width ranges from 1 to 10 miles (1.6 to 1 ...

Crow Wing County, Minnesota Crow Wing County is a County (United States), county in the East Central part of the U.S. state of Minnesota. As of the 2020 United States census, 2020 census, the population was 66,123. Its county seat is Brainerd, Minnesota, Brainerd. The cou ...

and named for

petrologist Petrology () is the branch of geology that studies rocks, their mineralogy, composition, texture, structure and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous an ...

Frank Fitch Grout (1880–1958), of the University of Minnesota.

References

Manganese(III) minerals Orthorhombic minerals Minerals in space group 62 {{oxide-mineral-stub