Good point. That’s the beauty of gold. It’s one of the most non reactive metals.
“Expect it to rust.” It occurs to me that the author may be thinking of seeing the clumps of silver and gold coins that are found by metal detector folks and archaeologists in the remains of 1,600 - 2,000 year old Roman sites in Britain. They tend to get tarnished laying in dirt that long opposed to these 180 year old gold coins immersed in salt water. I’m basing this on watching old “Time Team” archaeology shows from BBC4. eg:
https://www.youtube.com/watch?v=-RwpnQ4dWtk
https://www.imdb.com/title/tt0108961/