Grunerite
A variety of Minerals
What is Grunerite?
Grunerite is a mineral of the amphibole group of minerals with formula Fe7Si8O22(OH)2. It is the iron endmember of the grunerite-cummingtonite series. It forms as fibrous, columnar or massive aggregates of crystals. The crystals are monoclinic prismatic. The luster is glassy to pearly with colors ranging from green, brown to dark grey. The Mohs hardness is 5 to 6 and the specific gravity is 3.4 to 3.5. It was discovered in 1853 and named after Emmanuel-Louis Gruner (1809–1883), a Swiss-French chemist who first analysed it.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Grunerite 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.
Grunerite Localities Map
See where Grunerite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
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Quick Facts
Physical Properties
- Color
- nd
- Hardness (Mohs)
- 5 - 6
- Streak
- nd
Chemical Properties
- Chemical Formula
- {Fe2+2}{Fe2+5}(Si8O22)(OH)2 Grunerite is defined as a monoclinic amphibole belong to the magnesium-iron-manganese amphibole subgroup. It is defined with Fe2+ as the dominant element both in the B and C positions.
- Elements
- Fe, H, O, Si
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Grunerite FAQs
How do I identify Grunerite?
Grunerite can be identified by its hardness of 5 - 6 on the Mohs scale, nd color. Look for these key characteristics when examining specimens.
What color is Grunerite?
Grunerite typically appears in nd. Color can vary depending on impurities and formation conditions.
How hard is Grunerite?
Grunerite has a hardness of 5 - 6 on the Mohs scale. This gives it moderate hardness.
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