There are currently 3 resources that can be collected.
Titanite is a harder metal found in iron_ore. When mining iron_ore there is a chance you lose the iron but get a titanite ore instead.
Conduit is a goldish power conducting metal found in Gold Vines. When mining gold_ore there is a chance you lose the gold but get a Conduit ore instead.
Silicon is a mineral that can only be found in brain coral The warm ocean to be exact. the only way to get it is by mining Brain Coral Blocks.