What role does copper play in geomantic omen?

Very gold things, copper things are generally used to dissolve earth evil spirits (the symbol of Huang Wu's evil spirits or Erhei disease), as well as mascots to make money and treasure, such as golden toad, but they can only be placed where gold is needed.

If you need wooden things, you can't use copper things. So copper is not good.

Why use copper? Because it can be oxidized, the sound it makes will vibrate. These are the main principles and functions of evil spirits.

Brass and copper are the same as long as they are clean and not oxidized!