Figure 1. The GIA 7 Pearl Value Factors system classifies pearls according to size, shape, color, luster, surface, nacre, and matching. Composite photo by GIA staff. Prized by many cultures throughout ...

Rough pink diamonds are rarely found, and although the cause of color has been correlated with plastic deformation, the precise mechanism and atomic configuration for the resulting color are topics of ...

Gem-quality diaspore occupies an important position in the gem market due to its rarity, striking pleochroism, and color-change phenomenon (figure 1). The material’s value depends on these factors. A ...

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 ...

CARLSBAD, Calif. – August 26, 2025 – GIA, the Gemological Institute of America, will launch revised evaluation services for D-to-Z laboratory-grown diamonds on October 1. Current GIA laboratory ...

The Karowe Diamond Mine in Botswana, owned and operated by Lucara Diamond Corp., has gained international recognition for producing large, high-quality type IaB or coexistence of IaB with IIa diamonds ...

CARLSBAD, Calif. – June 2, 2025 – Beginning later this year, GIA (the Gemological Institute of America) will start using descriptive terms to characterize the quality of laboratory-grown diamonds and ...

Figure 1. Sapphires from Madagascar: a beautiful 3.29 ct untreated faceted stone and an assortment of rough in the background. Madagascar has produced many high-quality stones in the last few years ...

The micro-world of gems lies at the very core of gemology. Information gathered from observations through the microscope serves as the very foundation for many conclusions drawn on a specimen, ...

Figure 1. Top: These five opal slices of comparable thickness were cut from the same rough. They were semitransparent to translucent when viewed in daylight on a black background. Play-of-color was ...

Figure 1. This group of rock crystal quartz from Brazil shows vibrant blue dumortierite inclusions. The largest rough crystal weighs 139.79 ct, and the faceted stone weighs 15.47 ct. Photo by Kevin ...

Figure 1. A suite of nine rubies from the Rock Creek sapphire deposit in Montana. The stones range in weight from 0.172 to 0.578 ct. Photo by Kevin Schumacher, courtesy of Jeffrey R. Hapeman, Earth’s ...