Diamonds are the most amazing of gems. Just as amazing, however, is how natural diamonds reach Earth’s surface. Diamonds are formed 150 to 700 km deep in Earth, and are then carried upward in a rare ...

Figure 1. This demantoid was faceted to better reveal the “horsetail” inclusions. The sample is 8 mm in diameter. Photo by U. Hennebois. The exact origin and composition of the “horsetail” inclusions ...

Figure 1. Top left: Rubies are mined in a mango orchard in Channapatna, India. Top right: This 15 kg rough ruby is from Subramaniam, in the Indian state of Karnataka. Photos by Pooja Shirole. Bottom ...

The red variety of the mineral tugtupite, a rare silicate closely related to sodalite, has been used as a gemstone since 1965. This article presents the history of the mineral and details of its ...

Descending into Peshawar for the first time, a foreign tourist might be surprised to learn that amid the clutter of buildings in this historical city lies an important gem trading center. This market ...

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 ...

Diamonds are known for their hardness – their ability to resist scratches and abrasions. But diamonds are not impervious to damage, since their hardness is uneven along different crystal directions.

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 ...

This three-strand bracelet by Sally Agarwal, London, shows how old-style polki diamonds work well in new jewelry designs. The bracelet contains 87 polki cut diamonds, total weight approximately 11.85 ...

Figure 1. Glass in a silver brooch, hallmark from 1866. Private collection, photo by Jaroslav Hyršl. Tectites are members of a large group of impact glasses, formed by the collision of a meteorite on ...

This handful of crystals is just a small portion of the production we saw during our short visit to the Cruzeiro mine. These multicolored crystals range from rubellite to green, with black ...

A parcel of sapphire and chrysoberyl from the Ilakaka-Sakaraha deposit in southern Madagascar. Photo by Vincent Pardieu, © GIA. Introduction In July-August 2010 and ...