I've adapted some races from the Earthdawn rpg, as it's one of my all time favorite settings. This is the stonelike Obsidimen.
Obsidimen
+2 Str OR +2 Con
Racial Power:
Stoneskin: Start every battle with +2 AC & PD until you are hit by an attack.
Champion Feat: Whenever you spend a Recovery in battle, regain Stoneskin.