verdigris
Concise Oxford English Dictionary © 2008 Oxford University Press:
verdigris /ˈvəːdɪgriː, -griːs/
▶noun a bright bluish-green encrustation or patina formed on copper or brass by atmospheric oxidation.
– origin ME: from OFr. verte-gres, earlier vert de Grece ‘green of Greece’.
'verdigris' also found in these Oxford entries:

