Heavy armor includes: Iron, Steel, Dwarven, Orcish, Ebony, Daedric and Dragon.
Previous ES games always had an equal number of 'types'.
There is however a Smithing perk on the Light Armor branch of the skill tree that comes between Elven and Glass that states "Can create Scaled and Plate armor at forges, and improve them twice as much". The Scale doesn't refer to Dragonscale because that is clearly the the top perk for both branches. Does anyone know if Scale and a sort of Light Plate are armor types for Light Armor?
