This melee weapon has an actual metallic meteor as the head of the flail.
It can deal fire damage, but the real impact comes with a critical hit, and that's about the kinetic energy.
It's not specifically mentioned in the description, but the green color of the fire is because meteors falling through the atmosphere that contain a lot of nickel in them glow green. I saw one in person one night (relatively close), and it was an unusual sight.