The filling of surface-reaching breaks in emeralds is a relatively common practice, for which various kinds of oils and a natural resin have historically been used. Now, however, epoxy resins are replacing the more traditional fillers such as cedarwood oil and Canada balsam. The most widely known of these epoxy resins is sold under the brand name Opticon. The results of a broad study of various fracture-filling materials found that Opticon treatment (1) was, like the traditional materials, best detected using magnification with a variety of lighting techniques; and (2) although somewhat more durable than the traditional enhancements, was still altered in the course of routine jewelry cleaning and manufacturing processes. This article also examines the filling of surface pits with epoxies, the potential effectiveness of "dyed" Opticon, and the use of Opticon to fill the fractures in gem materials other than emerald.