The cast bronze with green patina on granite base is a unique sculpture by the artist. (1stdibs.com)
It was so dirty when I found it (and not the pretty green patina of copper, just plain old dirt). (whimsicalblueliving.com)
A low - voltage current runs between the two, freeing copper ions and collecting sodium and chlorine, creating a crusty blue - green patina on one pipe as the other slowly blackens and weakens. (marissaleebenedict.com)