Cornwallite
A variety of Minerals
What is Cornwallite?
Cornwallite is an uncommon copper arsenate mineral with formula Cu5(AsO4)2(OH)4. It forms a series with the phosphate pseudomalachite and is a dimorph of the triclinic cornubite. It is a green monoclinic mineral which forms as radial to fibrous encrustations.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Cornwallite 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.
Cornwallite Localities Map
See where Cornwallite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Formation of Cornwallite
It was first described in 1846, for an occurrence in Wheal Gorland, St Day United Mines of the St Day District, Cornwall, England. It occurs as secondary mineral in the oxidized zone of copper sulfide deposits. Associated minerals include olivenite, cornubite, arthurite, clinoclase, chalcophyllite, strashimirite, lavendulan, tyrolite, spangolite, austinite, conichalcite, brochantite, azurite and malachite.
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Quick Facts
Physical Properties
- Color
- Verdigis green, blackish-green, emerald-green; emerald-green in transmitted light.
- Hardness (Mohs)
- 4.5
- Density
- 4.64 g/cm³
- Streak
- Apple green
Chemical Properties
- Chemical Formula
- Cu5(AsO4)2(OH)4
- Elements
- As, Cu, H, O
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Cornwallite FAQs
How do I identify Cornwallite?
Cornwallite can be identified by its hardness of 4.5 on the Mohs scale, Verdigis green color. Look for these key characteristics when examining specimens.
What color is Cornwallite?
Cornwallite typically appears in Verdigis green, blackish-green, emerald-green; emerald-green in transmitted light.. Color can vary depending on impurities and formation conditions.
How hard is Cornwallite?
Cornwallite has a hardness of 4.5 on the Mohs scale. This gives it moderate hardness.
What is the formation of cornwallite of Cornwallite?
It was first described in 1846, for an occurrence in Wheal Gorland, St Day United Mines of the St Day District, Cornwall, England. It occurs as secondary mineral in the oxidized zone of copper sulfide deposits. Associated minerals include olivenite, cornubite, arthurite, clinoclase, chalcophyllite, strashimirite, lavendulan, tyrolite, spangolite, austinite, conichalcite, brochantite, azurite and malachite.
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