Mithral

Mithral is a rare, silvery metal that is lighter than steel but just as hard. An item made from mithral weighs half as much as the same item made from other metals. In the case of weapons, this lighter weight does not change a weapon's size category or the ease with which it can be wielded (whether it is light, one-handed, or two-handed). Mithral weapons count as silver for the purpose of overcoming damage reduction. Weapons fashioned from mithral are always masterwork items as well.