The term "alexandrite effect" refers to the apparent change of color in certain minerals from blue-green or greenish violet in daylight to red or reddish violet in incandescent light.

Thailand has become the world's major source of gem ruby.

The discovery and gemological properties of gem-quality friedelite.

The lapidary arts of Harold and Erica Van Pelt.

An examination of the challenges of carving gem-quality opal.

Gem-quality tugtupite has come almost exclusively from one occurrence.

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

An overview of the potential effects that heat treatment can have on corundum.

An overview of the many types of gem-quality material, and its inclusions, currently found in Sri Lanka.

How amethyst under certain conditions may turn green rather than the expected citrine-yellow.

An examination of the various simulants of of nephrite and jadeite, and how to separate them from jade.

The cutting of a one-kilo kunzite crystal demonstrates the problems inherent in working with this stone.

Marketed throughout the world, San Carlos material is often confused with, and sold as, peridot from localities that are better known and documented.

apis-lazuli is an ornamental stone (figure 1) that has been found in the artifacts of some of the oldest known civilizations.

The first substantiated identification of corundum (var. ruby) occurring as an inclusion in natural diamond is presented.

A discussion of the techniques important in producing top-quality photomicrographs.

A review of heat treatment methods available for use on natural or synthetic corundum.

A discussion of work being done to enhance color in gemstones, as well as techniques used at the California Institute of Technology to detect whether colors are natural or enhanced.

A comprehensive review of the history and geology of Colombian emeralds together with descriptions of some of the most famous gems to come from this locality.