Iron wurm

When you mine an Iron Node, there's a chance that a "Iron Wurm" will appear, a giant rock worm. When you kill this rock worm it will leave you a Wurm Tunnel. Enter this tunnel and you will find a cave filled with iron nodes. So far there seems to no way of knowing it will be an iron wurm inside your iron node. When one enters the tunnel, the time is running! It can be advised to make haste and collect as much ore as possible in those 2 (?) minutes inside the tunnel.