Arrows are split into 3 types, each made from a variety of each material.
Some materials use different shaft types. Damage is determined on both
design and material. some materials have bonus effects

Mithril arrows are lighter than others

Arrow types:
Normal: Standard everyday arrow, average damage
Bodkin: ligher more aerodynamic arrow, less damage, more range
Broad: Heavy and penetrating, does large damage and armour Penetration.

Bonus Effects
Silver: Devistate undead
Dragonforge: Flame
Ignotumite: Poison