Geigerite
A variety of Minerals
What is Geigerite?
Geigerite is a mineral, a complex hydrous manganese arsenate with formula: Mn5(AsO3OH)2(AsO4)2·10H2O. It forms triclinic pinacoidal, vitreous, colorless to red to brown crystals. It has a Mohs hardness of 3 and a specific gravity of 3.05. It was discovered in Grischun, Switzerland in 1989. It was named in honor of Thomas Geiger (1886–1976), Wiesendangen, Switzerland, who studied the Falotta manganese ores.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Geigerite 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.
Geigerite Localities Map
See where Geigerite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Composition of Geigerite
The chemical composition of geigerite is hydrous manganese arsenate (Mn5(AsO3OH)2(AsO4)2·10H2O). The chemical composition was found by using an electron microprobe in the Falotta mines in Switzerland.
Quick Facts
Physical Properties
- Hardness (Mohs)
- 3
Chemical Properties
- Chemical Formula
- Mn2+5(AsO4)2(HAsO4)2 · 10H2O
- Elements
- As, H, Mn, O

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Geigerite FAQs
How do I identify Geigerite?
Geigerite can be identified by its hardness of 3 on the Mohs scale. Look for these key characteristics when examining specimens.
How hard is Geigerite?
Geigerite has a hardness of 3 on the Mohs scale. This makes it a soft mineral that can be scratched easily.
What is the composition of geigerite of Geigerite?
The chemical composition of geigerite is hydrous manganese arsenate (Mn5(AsO3OH)2(AsO4)2·10H2O). The chemical composition was found by using an electron microprobe in the Falotta mines in Switzerland.


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