Basically, to allow for crazy things like swords of fire, dragonbone armor, etc, would it be feasible to create arbitrary material forms? Each material affecting the equipment differently, possibly going beyond weapons and armor. I mean theres probably a reason why wands are made of gold or magic scepters are made of solid ruby.

I figure it probably shouldn't be TOO crazy with a class-like structure.
Something like:
Material
-Metal
--Ferrous
---Iron
---Steel
-Energy
--Lightning
--Fire
-Stone
--Granite
--Crystal
---Diamond
---Ruby
-Organic
--Wood
---Oak
--Bone
---Creature Type
--Leather
---Creature Type