Following up on Nassau's 1981 article on the technical aspects of heat treating ruby and sapphire, the author reports his personal observations of the actual heat treatment process in Bangkok. He ...

Since Robert Crowningshield's discovery in the late 1950s that diamonds that have been artificially colored by irradiation and subsequent annealing could be identified by their characteristic ...

Figure 1. This suite of untreated emeralds is from a new find in Ethiopia’s Seba Boru district. The largest faceted stone weighs 10.64 ct. The largest rough crystal weighs 63.12 g. Photo by Robison ...