Metrology, the science of measurement and its application, plays a critical role in the accuracy of GIA’s research and laboratory services. The metrology team closely monitors the performance of ...

Diamonds have a long history as a premier gemstone—a natural consequence of their beauty, rarity, and superlative physical properties such as extreme hardness. Diamonds that are mined for use as ...

Figure 1. This gold ring with a phoenix motif features a Neyshabur turquoise (13 × 17 mm), with a 0.02 ct ruby on each side and diamond accents. Courtesy of Taktala Jewelry, Tehran. Turquoise is an ...

This chart focuses primarily on the types of natural inclusions found in tourmaline, as well as the minerals in which tourmaline can be found as an inclusion. Treatments such as enhancement of ...

Jadeite jade is one of the most important aggregate gems in today’s global marketplace, with known sources in Myanmar, Japan, Russia, and Guatemala. Among them, Myanmar is the most legendary and still ...

Phoebe Shang, a senior writer at GIA, is a Graduate Gemologist. Wim Vertriest is Manager of Field Gemology for GIA, Bangkok. Since joining GIA’s Field Gemology Department in 2015, Wim has visited ...

A crystal and cut stone of Imperial Topaz from the Vermelhão mine near Ouro Preto in Minas Gerais, Brazil. Photo by Robert Weldon, courtesy of Bill Larson and Edward ...

Figure 1. Corundum is an example of a negative uniaxial mineral. This ruby crystal in matrix from Mogok, Myanmar, is approximately 6.15 cm in length. The cut gem is a 3.22 ct unheated ruby, also from ...

Earth’s surface is divided into tectonic plates, and the ones that make up the ocean floor are destined to sink. Sheets of oceanic crust typically bend and sink down into Earth’s interior at so-called ...

“Rabbit hair” quartz is a commercial variety of quartz with special inclusions. These inclusions resemble rabbit fur and are shorter and thinner than the typical rutile, tourmaline, or other acicular ...

Carved single-crystal diamond rings are rare, with few examples to reference (see Spring 2020 Lab Notes, pp. 132–133). But with advancing technology in the laboratory-grown diamond industry, the ...

Figure 1. Five loose “Edison” Chinese freshwater cultured pearls (11–14 mm) surrounded by a 17-inch necklace featuring variously colored round Edison pearls (10.5–13.5 mm). Photo by Robert Weldon/GIA, ...