I found what I believe is a small piece of petrified wood today on the Donghe beach, near where they were recently doing construction of some sort. (What the heck were they doing?) I assume this was unearthed during the construction/destruction on the beach.

According to the information on Wikipedia (http://en.wikipedia.org/wiki/Petrified_wood), the colors suggest that the piece is largely made up of iron. Indeed it looks like it has specks of rust on it. It smells metallic, with a hint of sulfur.