Color types such as "pigeon's blood," "Paraíba" and "cobalt blue" have become wildly popular in the gem trade. But there is a vast difference between coining such terms and applying them in a way that is both consistent and logical. Richard Hughes casts a critical eye at the subject.

How does one go about choosing a good gem testing lab? The gemologists at Lotus Gemology provide the following guide to help customers make the best decisions when choosing a good gem testing lab.

Detection of heat treatment below 1200°C in ruby and sapphire can present challenges to gemologists. In this study, the authors heated Burmese ruby samples and detailed the features that help in the detection of heat treatment.

A truth that's told with bad intent, beats all the lies you can invent.

—William Blake [1757–1827], Proverbs, Line 95

When a red spinel and a tanzanite were submitted for testing, oil was found in the fissures. Removal of the oil resulted in a startling deterioration in clarity.

Short-wave fluorescent illumination provides a useful tool to spot curved banding in flame-fusion synthetic sapphire.

Some yellow sapphires contain unstable color centers. The following discussion outlines case studies of stones that faded after testing in the lab, and how color may be restored.

Blue apatite crystals in garnet.

An apatite crystal appears to float, suspended over a rutile silk cloud in a star sapphire.

Oil treatment has a significant impact on the appearance of an apatite.