Diamondhead's body is composed of an extremely dense and durable organic crystal, making him nearly invulnerable. He can manipulate the atomic structure of his diamond physiology at will, allowing him to create crude crystal weapons from any part his body on demand or fire crystal shards from his hands. In certain ways, he can reshape his projectiles into certain shapes. He can even control those that are not connected to his body. This same ability also allows him to regenerate to an extent, such as regrowing lost limbs.
In addition to growing crystal from himself, Diamondhead can grow crystal over other objects. In the episode, Vengeance of Vilgax: Part 2, Ben as Diamondhead, seems to levitate three pillars of crystal that he controls to aim toward Vilgax, defeating him. Lasers and other similar weapons are useless against Diamondhead, as his crystal body acts as a prism, refracting the beams. He also has proved strong enough to easily beat Kevin, defeat Vilgax, and smash apart various objects with relative ease(an example of this is when he mutilated a semi truck just by sneezing). The one drawback to Diamondhead's crystal form is the crystal itself, which can shatter if exposed to sufficiently strong sonic vibrations. Though his diamond structure is durable, it can be damaged with sufficient force. While Petrosapiens can regenerate limbs, there is a limit to how much damage they can recover from. He also seems to be able to survive if shattered, given his head is still intact.