This large Australian light opal cabochon weighs 117.85 carats. Small play-of-color flashes of orange and green predominate in a pinfire pattern, with spots of a more muted blue over a grayish ...

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.

For the first time ever, the famous Hope diamond was graded by a widely recognized system. Although the 45.52-ct weight was confirmed, the GIA Gem Trade Laboratory graders found the clarity—recently ...

Figure 1. The bright red faceted ruby in this gold ring is from the large and potentially productive Snezhnoe deposit in Tajikistan. Photo by Zamoniddin Z. Nasriddinov. Discovered during the late ...

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 ...

A new diamond imitation, synthetic moissanite (silicon carbide), is now being produced by C3 Inc. in near-colorless form for jewelry purposes. With refractive indices of 2.648 and 2.691, a dispersion ...

Figure 1. The color zoning of amethyst from Boudi often displays a characteristic hourglass shape. Photo by Abdelghani El Harfi and Salahaddine Mouaddib. For 25 years, the Moroccan locality of Boudi ...

Lapis lazuli is an aggregate of several minerals. Lazurite grains provide its characteristic blue color, while golden flakes of pyrite can add attractive contrast. Lapis lazuli is a rock, which means ...

Natural pearls grow in the wild without human intervention. They are very rare, and most natural pearls in the market today are antique. Cultured pearls are grown in pearl farms, and are the direct ...

Figure 1. Schematic representation comparing PL methods. With standard PL microscopy, a single spot (shown as a green circle in the figure) is analyzed and represents only a small volume of the actual ...

The GIA Gem Trade Laboratory (GTL) collected gemological data on 1,490 natural-color pink gem diamonds—both types I and II. While there was some overlap in gemological properties between the two ...

Jadeite is 6.5 to 7, and nephrite is 6 to 6.5 on the Mohs hardness scale. Hardness and toughness Gem and mineral hardness is measured on the Mohs scale. The numbers are based on the relative ease or ...