Commercial quantities of gem-quality benitoite are known from a single location in the world, the Benitoite Gem mine in the New Idria district of San Benito County, California. A barium titanium ...

Examination of red and blue samples of a relatively new flux synthetic spinel from Russia established criteria by which they can be separated from their natural counterparts. The flux synthetic blue ...

Diamond “type” is a concept that is frequently mentioned in the gemological literature, but its relevance to the practicing gemologist is rarely discussed. Diamonds are broadly divided into two types ...

Figure 1. Pleochroism in a 15 ct tanzanite, as seen with the unaided eye through the crown and the pavilion sides and ends. Photo by Wimon Manorotkul. In describing colored gemstones, the major ...

The GIA Laboratory-Grown Diamond Report includes full quality assessment with a plotted clarity diagram. Color and clarity specification are described on the same scale as the GIA Diamond Grading ...

As a consumer, you will regularly encounter in the marketplace gems that have been treated to change their appearance. A topic that often comes up is whether a particular gemstone is or isn’t treated.

Figure 1. These emeralds from Musakashi, Zambia, range from 0.57 to 4.85 ct. The rough samples were polished with one window on each. The faceted sample measures 6.29 × 5.35 × 3.53 mm and weighs 0.97 ...

Emerald, the birthstone for May, has been beloved for millennia, evoking rebirth and renewal. Widely regarded as the definition of green, emerald is the perfect color for spring. From the poetic ...

If you were born in the month of June, you are lucky enough to have three birthstones to call your own. June is one of only three months (the others are August and December) that has three birthstones ...

Consumers now, more than ever, have a heightened awareness of sustainably and ethically sourced products. The GIA Diamond Origin Report uses scientific evaluation to provide confirmation of a ...

In 2009, GIA bestowed its highest honor, the Richard T. Liddicoat Award for Distinguished Achievement, on longtime chief research gemologist John I. Koivula. The award was based on his contributions ...