Verdigris (noun)

A bright blue-green patina formed on copper, brass, and bronze by atmospheric oxidation, often used as a pigment.

Origin:

Late 16th century: from french vert de gris, literally "green of greece", from vert "green" + gris "gray".

Examples:

1. The statue had developed a thick layer of verdigris over the years.
2. Verdigris is a common problem for copper roofs and gutters.
3. Verdigris is used as a pigment in paint, ink, and dyes.
4. The verdigris on the statue gave it a unique and interesting appearance.
5. Verdigris can be removed by cleaning the metal with a solution of vinegar and salt.