As of now, the Crozius Arcanum is listed as "S as User, AP3, Melee" which is the statline for a Power Sword or unique weapon, though the new rulebook states that a Crozius Arcanum should be treated as a Power Maul (S+2, AP4, Melee, Concussive).
I checked the Codex Space Marine chaplains as well as the Black Templar ones, and it was the same, so I'm assuming its the same for all Marine armies.
