Ophealine

Ophealine, or more commonly glass stone, was the name in the Realms for axinite. The purple or violet variety was called yanolite.

Description
Ophealine occurred in large crystals that yielded faceted gemstones of impressive size, and was hard enough to be used in jewelry, especially rings, that were subject to the wear and tear of everyday use. The typical brown hue was so intense that bigger crystals looked opaque. Unfortunately, brown was not in great demand as a gemstone color, but glass stone found its way into rings because it could hold a sharp edge and survive a good bar fight. In Waterdeep, the street name for such items was "knuckle stones". A typical stone had a base value of 10 gp.

Powers
Ophealine had an anti-magic quality such that it could not be used as a material component in any spell, potion, ink or other magical preparation&mdash;the magic always failed. When worn as an ornament, ophealine prevented hold person spells and all manner of magical paralyzing effects from being effective.