Chrysoberyl

Chrysoberyl is a hard, transparent, green gem, ususally facet-cut. Chrysoberyls are used in producing devices which provide protection against magic jar spells or other forms of possession, and in weapons designed to affect ghost and similar creatures. A typical specimen has a base value of 100gp.

A chrysoberyl gem could be used for short-range but very detailed scrying. For that reason, it was known as a "cat's eye."