CS Book 3 _AS-13 Blue Sapphire.pdf

Blue Sapphire KEY CONCEPTS Trade members and consumers often use the single word “sapphire” to describe the blue variety of corundum. Fine-quality, untreated sapphires make up a small but extremely valuable segment of the sapphire market. Blue sapphire is one of the most popular colored stones, espe...

Blue Sapphire KEY CONCEPTS Trade members and consumers often use the single word “sapphire” to describe the blue variety of corundum. Fine-quality, untreated sapphires make up a small but extremely valuable segment of the sapphire market. Blue sapphire is one of the most popular colored stones, especially in the US. Madagascar has become a significant source of good- to finequality blue sapphire. The most highly valued blue sapphires are velvety blue to violetish blue, in medium to medium-dark tones, with strong to vivid saturation. Most fine sapphires over 100 carats are from Sri Lanka. The trace elements iron and titanium cause the blue of sapphire. Higher levels of iron make basalt-related sapphires darker than non-basaltic sapphires. The trade term “Kashmir” refers to what many consider the finest blue sapphires. Cutters must consider color zoning, a common sapphire characteristic. Most blue sapphires are heat-treated to improve their appearance. Heat-treated geuda and dhun make up a significant portion of the commercial-quality blue sapphire market. Kashmir sapphires owe their reputation to a brief period of output in the 1880s. Thailand is a major center of the corundum trade, funneling a steady flow of gems from worldwide sources into the consumer market. Australia is one of the world’s major sources of dark blue, commercial-quality sapphires. Yogo Gulch sapphires are characterized by small size and saturated blue color, and do not require heat treatment. US consumers buy about half of the blue sapphires on the world market. Thailand is the leading exporter of sapphire to the United States by volume and value. Flame fusion is the most common sapphire synthesis method. 131