Figure 1. Left: 18K yellow gold “Flames” ring with 25.19 ct Mexican fire opal. Right: This 18K yellow gold “Spice” ring ...

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 ...

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 ...

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 ...

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, ...

Abalone is the common name of the marine mollusk species that belongs to the Haliotis genus. Various abalone species are distributed worldwide along cold coastal waters. They live in rocky habitats, ...

Chemical vapor deposition (CVD) growth technology has advanced significantly over the last two decades. In this study, we report on the largest CVD gem diamond GIA has encountered, recently tested in ...

In November 2022, a parcel of 24 approximately 0.5–1.2 ct spinel crystals, described as cobalt-diffused, were obtained directly from a treater by the research team at GIA in Bangkok. Of these, seven ...

Le Ngoc Nang, Pham Minh Tien, Pham Minh, and Pham Trung Hieu Anorthoclase, (Na,K)AlSi 3 O 8, is an uncommon variety of alkali feldspar that is the potassium-rich variety of high albite, distinguished ...

Although today’s global freshwater cultured pearl market is mostly dominated by Chinese products, Japanese freshwater pearl cultivation started in 1935. Lake Biwa in Shiga Prefecture supplied pearls ...