A relatively new production of red corundum, reportedly from Bangkok, has been offered for sale in recent years. Although the producers claimed that these stones were red diffusion-treated corundum (i ...

A look at the history of analytical instruments used for gem testing. UV-Vis-NIR spectroscopy measures how gemstones absorb and interact with light across the ultraviolet, visible, and near-infrared ...

Cultured pearls come in different sizes, shapes, and colors. Perhaps the best-loved gems of all time, pearls—both natural and modern cultured pearls—occur in a wide variety of colors. The most ...

The Diamond Trading Company (DTC) Research Centre had the opportunity to examine a diamond that, on submission to a commercial gem laboratory, was stated to have been HPHT treated. However, ...

“Rainbow” andradite from Nara, Japan, occurs as relatively small orangy brown crystals that show attractive iridescence in almost the entire range of the spectrum. The material is nearly pure ...

GIA is the creator of the 4Cs of diamond quality and the leading research and education center for gems and gemology. Considered the world authority on gems, the Institute is open to the public Monday ...

Figure 1. The sparsely populated high desert of eastern Oregon is home to three localities producing natural copper-bearing labradorite feldspar. In this view of Lake County’s Dust Devil mine, the ...

The discovery of significant quantities of gem-quality sapphire in Minas Gerais could add corundum to the formidable list of gem species already commercially produced in Brazil. The presence of ...

In January 2012, aquamarine crystals containing interesting inclusions were extracted from the Ambatofotsikely area northwest of Antsirabe, Madagascar. These specimens displayed various types of ...

Figure 1. These 20 completely non-nacreous pen pearls, from the group of 22 samples in this study, are set against a pen shell displaying both nacreous (left) and non-nacreous areas (right). Photo by ...

During the last 20 years, Australia has assumed a major role in the production of blue sapphire. Most of the gem material comes from alluvial deposits in the Anakie (central Queensland) and New ...

A new microlithography process developed to create high-resolution diffraction grating patterns on portions of certain facets can improve the dispersion of light and thus the amount of “fire” in a ...