Pale-Sodium

Pale-Sodium, archaically known as Witch's Bane, is the counter ore to White-Mercury and has the power to cut off a wizard's magic when it is exposed to his or her bare skin. Unfortunately for wizards, pale sodium is a fairly common magical ore and certain magical compounds such as charged gypsum and even to a much lesser degree pure salt can also have an adverse effect on their magic. Pale-sodium is a soft, pliable metal and starts off pure white then quickly fades to a dark gray as it decays and looses potency. Depending on how much magic it is exposed to, pale sodium it will last between three weeks and five months, before decaying into mundane sodium. Magical verity gypsum is a soft flakily stone and decays even faster than pale-sodium, darkening in only a few days. Both sodium and gypsum are too soft to make into any kind of armor or weapon, but they have be used to line shackles and can be formed into a pendant which can be worn around the neck. There have also been incidences where it as been dissolved or crushed into poisons to be drunk or eaten.

((Borrowed from Syme's profile.))