Explore tourmaline history, research, quality factors, and more in the GIA Gem Encyclopedia.

Whether you're taking your next step in your professional journey or starting a new career, GIA courses and diploma programs prepare you for success. With curriculum developed from groundbreaking ...

Asteriated synthetic rubies and sapphires were produced by Wiede’s Carbidwerk of Freyung, Germany, between the mid-1950s and the end of the 1970s. The rough crystals were grown slowly through a ...

Major rock units of the Neyshabur mine are divided into three groups: volcanic, subvolcanic intrusions, and hydrothermal breccia (Ghiasvand et al., 2017). Although the volcanic rocks of trachyte and ...

Figure 1. A comparison of the Mohs hardness scale and the Knoop hardness scale, a micro-hardness test where a pyramidal diamond point is pressed into the polished surface of the sample with a known ...

This 32” x 20” wall chart presents GIA’s system for classifying pearl quality according to the seven factors of size, shape, color, luster, surface, matching, and nacre.

As part of this service, a gold bracelet measuring 8 inches in circumference and 1.25 inches wide and weighing 41 g was recently examined in the Carlsbad laboratory (figure 1). It was submitted as 14K ...

Explore diamond history, research, quality factors, and more in the GIA Gem Encyclopedia.

Yellow is the most abundant color of natural fancy diamonds, yet they still represent a very small percentage of all diamonds. The first major source of yellow diamonds was found in the late 1860s in ...

The Fall issue of Gems & Gemology provides a glimpse into the future of gemology, with a paradigm-shifting approach to assessing fancy-shaped diamonds, the use of machine learning algorithms in gem ...

Part 4 of 5 in the series: Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond). This article digs deeper into cutters’ choices and explores additional factors used in the trade ...

ABOUT GIA An independent nonprofit organization, GIA (Gemological Institute of America), established in 1931, is recognized as the world’s foremost authority in gemology. GIA invented the famous 4Cs ...