Euchroite

 Euchroite is a hydrated copper arsenate hydroxide mineral with formula: Cu2AsO4OH·3H2O. It is a vitreous green to emerald green mineral crystallizing in the orthorhombic system. It has a Mohs hardness of 3.5–4.0 and a specific gravity of 3.39–3.45. It was first described in 1823 in Ľubietová, Slovakia.