The final part of this series is concerned with colors explained by band theory, such as canary yellow diamonds, or by physical optics, such as play-of-color in opal.

The gemological properties of a new ruby imitation, produced by dyeing natural colorless to pale-colored corundum, are described.

Northern Vietnam began producing significant quantities of rubies and fancy sapphires in the late 1980s.

The history of Baja California has been closely tied to the exploitation of pearls since the 16th century.

Mina Stones promotes Nigerian gems including rubellite and sapphire as well as reviving traditional skills and symbols in the creation of original jewelry.

A nondestructive rapid screening technique uses fluorescence spectroscopy to identify treated colored pearls.

Application of slight pressure perpendicular to the twinning planes reveals the unusual property of this synthetic gem.

Gamma ray spectroscopy revealed that a packet of spodumene from Brazil was radioactive.

The history of the Kashmir mines, the beautiful sapphires found there, and the outlook for the future.