Gem Testing • Gemology Books, Articles from Lotus Gemology

The word "jade" often evokes the green jadeite used in jewellery. However, some of the most valuable jade in China is not this green jadeite, but in the creamy "mutton fat" carved nephrite from Hetian, Xinjiang province. In the past, many carvings touched upon familiar motifs like dragons or religious symbols, while in recent decades there has been a revolution of carving, with artists incorporating modern themes and styles into their work. Lin Tze-Chuan, an influential collector and patron of many jade carvers, is considered by many to be the father of Chinese contemporary jade carving. Here he discusses the changing world of jade carving and what he looks for when commissioning new work.

The world sapphire market has changed dramatically in the past 40 years. The authors review the famous sources of the past and look at the current situation in sapphire around the globe.

Madagascar has become one of the world’s top sources of fine blue sapphire in recent times. In addition to beautiful untreated material, increasing numbers of treated stones have appeared in the market. Some have been heated to relatively low temperatures, below 1350°C, to lighten their color. To help separate unheated and heated Madagascar sapphire, the authors performed experiments to document the changes they undergo with low-temperature heat treatment in air, which is an oxidizing atmosphere.

This excerpt from Ruby & Sapphire: A Gemologist's Guide (2017) details the ruby and sapphire deposits of Madagascar. Since the mid-1990s, Madagascar has become one of the world's most important sources.

To the jeweler, spinel is famous for its vivid colors. But for the gemologist, this gem is unlike any other. Its extreme hardness allows a fine polish. Couple this with single refraction, which eliminates the image blurring found in most other gems, and a varied landscape of inclusion subjects, and the result is an unparalleled canvas of delight for the photomicrographic artist.

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.