The ball looks very good.

I don't know where you can find corroded gold, maybe some miners can have gold reacting with mercurium images. A friend of mine cleaned a Mexican gold coin, the coin looked beatiful with the shining gold, but he discovered that the coin lost most of its value. He aged the coin with chemical at the University laboratory and the coin returned to its original value.

Egyptians had fun with electricity, so they could make corroded gold, but this was beyond the capabilities of the people in the Bible, so probably the covenant ark looked as normal gold and not as in the image that I have referred.

Stupidity also evolves!