Moonsilver

From the White Wolf Wiki, the most complete White Wolf reference

Moonsilver is a special form of silver that can only be obtained by completing a quest for the lunar Incarna. Moonsilver does twice as much damage to creatures vulnerable to silver. Unlike normal silver, it increases the Gnosis of the user rather than decreasing it.

It is extremely hard to obtain and only the greatest of Garou will be found worthy of an item made of it. Luna, Phoebe, Sohkta, or any of the faces of the lunar Incarna will punish unworthy Garou for misusing the substance.