ver·di·gris 
(vûrdĭ-grēs′, -grĭs′, -grē′)
(vûrdĭ-grēs′, -grĭs′, -grē′)n.
1. A blue or green powder consisting of basic cupric acetate used as a paint pigment and fungicide.
2. A green patina or crust of copper sulfate or copper chloride formed on copper, brass, and bronze exposed to air or seawater for long periods of time.
[Middle English vertegrez, from Old French verte grez, alteration of vert-de-Grice : verd, green; see VERDANT + de, of (from Latin dē; see DE-) + Grice, Greece.]
verdigrisdetail of a bronze equestrian statue of Joan of Arc in Meridian Hill Park, Washington, DC