The black onyx

A single black onyx, large and without a flaw in it, taken off the erratic woman where she fell in the street. Unscuffed and unchipped. She was carrying no coin at all, anywhere on her, and this instead.

Nobody has put a price on it. The party set it aside for Gemsmith to appraise and kept it deliberately out of the bag the rest of their stones travel in, where it has stayed.