He made two designs for the formation breaker. The first one is in the shape of a prismatic needle. The second one is the shape of a flat circular disc.
The prismatic needle was designed for penetrating barrier formations. When he was designing it, Arthur envisioned a nail that would be driven into a formation for breaking it.
But Arthur changed his mind and decided to use the flat circular disc shape to maximize the surface area of the formation breaker that will make contact with any kind of formation.
Both designs have their merits and demerits. The prismatic needle design has a more powerful formation-breaking potential because it has the ability to literally penetrate a formation, drive itself into it, and break it.
The needle design grants it a physical shape that can be taken advantage of to apply physical pressure on a formation and increase the chances of breaking it.
