Cornwallite
![](/Images/godic/202501/06/Cornwallite-1789553642.jpg")
![Botryoidal, green cornwallite in a gossan with white baryte from Caldbeck Fells, Cumbria (7.6 x 5.1 x 4.7 cm)](/Images/godic/202501/06/Cornwallite-Baryte-541933642.jpg")
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.