David McKinney, Naval Academy spokesman. The dome’s green patina will disappear when a new copper dome is installed. It will take 20 to 25 years for the dome to turn green again. Officials do ...

When I returned to the car, I left the detector on out of habit. At some point, there was a signal. When I was digging up the forest floor, I saw a flat metal object covered with green patina.

Through a series of oxidation reactions, a thin, green-blue layer known as a “patina” forms over copper as it is exposed to air. Not only did this process impart a markedly different color ...