Groutite
A variety of Minerals
What is Groutite?
Groutite is a manganese oxide mineral with formula MnO(OH). It is a member of the diaspore group and is trimorphous with manganite and feitknechtite. It forms lustrous black crystals in the orthorhombic system. It occurs in weathered banded iron formations, metamorphosed manganese ore bodies and hydrothermal ore environments. It was first described in 1945 for an occurrence in the Mahnomen mine, Cuyuna Range, Crow Wing County, Minnesota and named for petrologist Frank Fitch Grout (1880–1958), of the University of Minnesota.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Groutite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Quick Facts
Physical Properties
- Color
- Black, may be iridescent
- Hardness (Mohs)
- 3.5 - 4
- Rock tumbling
- Not recommended
- Density
- 4.172 g/cm³
- Streak
- dark brown
Chemical Properties
- Chemical Formula
- Mn3+O(OH)
- Elements
- H, Mn, O
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Groutite FAQs
How do I identify Groutite?
Groutite can be identified by its hardness of 3.5 - 4 on the Mohs scale, Black color. Look for these key characteristics when examining specimens.
What color is Groutite?
Groutite typically appears in Black, may be iridescent. Color can vary depending on impurities and formation conditions.
How hard is Groutite?
Groutite has a hardness of 3.5 - 4 on the Mohs scale. This gives it moderate hardness.
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