Witherite

Witherite was a yellow to white semi-precious gemstone.

Description
Witherite was found in large, fibrous deposits containing zones of translucent gem-quality material. If large enough, they yielded faceted pale yellow to whitish gems. Rarely, witherite occurred in clusters of translucent yellowish crystals which also yielded faceted gemstones. A typical specimen had a base value of 50gp.

Powers
Witherite gave some protection or even immunity to the withering effects of necromantic reversed healing spells and certain psionic attacks. The stone had to be mounted in a special electrum setting that allowed direct skin contact with the witherite. This was known to work for at least humans and demihumans.