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 ...

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 ...

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 ...

Southeast Vietnam has a total area of 23,000 km 2, and approximately 10,000 km 2 is covered by basaltic formations with thicknesses ranging from a few meters to over a hundred meters (figure 2) (Hoang ...

HISTORY OF FRESHWATER PEARL CULTURING IN JAPAN. Lake Biwa. Freshwater pearl culturing dates as far back as the thirteenth century, when pearls bearing Buddhist images and hemispherical pearls were ...

Beginning in the 1940s, the well-known European gemologist Eduard Gübelin began publishing a series of important articles in Gems & Gemology and Journal of Gemmology on inclusions and the evidence ...

Figure 3. Formation of the pink-brown eclogitic diamonds at Argyle—the world’s largest diamond deposit. After their formation, Argyle pink-brown diamonds resided in the high-temperature, ...

Laboratory-Grown Diamonds. Man-made diamonds suitable for industrial use were first produced in a laboratory in the 1950s. While gem-quality diamonds were produced in a laboratory for the first time ...

Photo: Robert Weldon/GIA Part 1 of 5 in the series: Value Factors, Design, and Cut Quality of Colored Gemstones (Non-Diamond) Originally published in GemGuide in 2016, this comprehensive series ...

Gem-quality synthetic or laboratory-grown diamonds are more available in today’s jewelry marketplace than ever before, causing both interest and concern about lab-grown diamonds and whether ...

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.

THE SMITHSONIAN The Smithsonian Institution is the world’s largest museum and research complex. Located on the National Mall in Washington, D.C., the complex includes 19 museums and galleries, the ...