What is the ruling on using copper rods to search for gold and metals underground, and is that considered a form of divination, bearing in mind that their effectiveness has been proven by experience, and that Sheikh Ibn Baz permitted their use for searching for water?

We are not aware of the fatwa attributed to Sheikh Ibn Baz. It has been stated in the fatwas of the Permanent Committee that testing the earth with modern devices to ascertain what is beneath its surface is not a form of soothsaying or claiming knowledge of the unseen. Rather, it is a way of understanding causes through their effects, and it aligns with God's cosmic laws. However, informing about what is beneath the earth based on mere conjecture without scientific reasons is deceit. Therefore, if it is proven through experimentation that copper indicates the location of gold, then there is no harm in using it.