Castellaroite
A variety of Minerals

What is Castellaroite?
Castellaroite is a rare arsenate mineral with formula Mn3(AsO4)2•4H2O. It is related to the phosphate mineral metaswitzerite. Castellaroite is monoclinic, with space group P21/n. The other natural manganese arsenate hydrate is manganohörnesite, which is an octahydrate.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Castellaroite 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.
Castellaroite Localities Map
See where Castellaroite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- colorless
- Hardness (Mohs)
- 3.5
- Density
- 3.164 g/cm³
- Streak
- white
Chemical Properties
- Chemical Formula
- Mn2+3(AsO4)2·4H2O
- Elements
- As, H, Mn, O

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Castellaroite FAQs
How do I identify Castellaroite?
Castellaroite can be identified by its hardness of 3.5 on the Mohs scale, colorless color. Look for these key characteristics when examining specimens.
What color is Castellaroite?
Castellaroite typically appears in colorless. Color can vary depending on impurities and formation conditions.
How hard is Castellaroite?
Castellaroite has a hardness of 3.5 on the Mohs scale. This gives it moderate hardness.


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