With proper care, citrine is a beautiful and versatile gemstone for jewelry use. – Robert Weldon Gem and mineral hardness is measured on the Mohs scale. The numbers are based on the relative ease or ...

A chart is provided that describes those gemological properties that are key to the separation of gem-quality yellow, blue, and near-colorless (to colorless) natural diamonds from synthetic diamonds.

Scientific advances in the past decade have completely altered our understanding of certain concepts relating to the age and origin of diamonds. As a generalization, most diamonds formed more than 990 ...

Despite the commercial value of natural-color diamonds, distinguishing them from treated diamonds remains a significant identification challenge. While some diagnostic visual features exist ...

The laboratory of the National Gold & Diamond Testing Center (NGDTC) encountered some plagioclase (moonstone) beads with blue adularescence. Fifteen of the 22 moonstones fluoresced moderate to strong ...

One of the greatest concerns with emerald filling is the degree of clarity enhancement such treatment represents. Stones that appear to have excellent clarity with the unaided eye are often revealed ...

Although the Art Deco period extends roughly from 1910 to well into the 1930s, it was primarily a product of the "Roaring '20s." This was a wonderfully decadent era. It was an age of Prohibition and ...

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 ...

Fancy color diamonds are among the rarest and most valuable gemstones. Diamonds in the normal color range are colorless through light yellow and are described using the industry’s D-to-Z color-grading ...

Aquamarine, Maxixe-type (irradiated) beryl, and two types of hydrothermally grown synthetic blue beryl currently available in the marketplace were investigated by classical gemological methods, ...

Figure 1. Six of the 13 cuprian liddicoatite tourmalines from this study. The faceted stones weigh 1.59–9.63 ct (average 3.95 ct). They are transparent and have greenish blue, green-blue, and green ...

With the withdrawal of Soviet troops from Afghanistan, villagers in the Panjshir Valley are turning their attention to the emerald riches of the nearby Hindu Kush Mountains. Large, dark green crystals ...