If you walk around enough cemeteries, you’ll notice that many statues and monuments have metal that has taken on a distinctive blue-green hue, just like the Statue of Liberty. If you’re like me, you learned about why this happens in some middle school science class and then promptly forgot. So if you already know this answer, you can skip the rest of this paragraph and just look at the pretty pictures. But for those of you who pushed out this science knowledge to have more room to remember the names of all the Muppets and the entire script of The Princess Bride, stay with me. The metal monuments and statues and plaques that go green because the alloys they are made of contain copper. When copper is exposed to water, it oxidizes and forms a layer that actually protects the metal underneath from degrading further. The patina and color are called verdigris.
A Grave Concern 