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Gemstones

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Suite containing over 36 carats of Yogo sapphire
Gemmological Characterisation of Sapphires from Yogo Gulch, Montana

A look at the mining and distinguishing characteristics of this naturally vibrant blue sapphire.

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Figure 1. One of GIA’s new LA-ICP-MS corundum calibration standards sets (set number 1); the epoxy disk containing the set is 1.5 inches in diameter. NIST SRM 610 and 612 glass standards are included to account for trace and non-trace elements, such as those found in inclusions, that were not incorporated into the synthetic sapphire crystals grown for standards. Photo by Jennifer Stone-Sundberg.
Accurate Reporting of Key Trace Elements in Ruby and Sapphire Using Matrix-Matched Standards

Presents a group of corundum standards developed by GIA to improve the accuracy and efficiency of its laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) instruments.

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Beryllium Diffusion of Ruby and Sapphire

The heat treatment of corundum involving lattice diffusion of beryllium (Be) at temperatures over 1800°C has become a major issue in the gem trade.

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Sapphires from Antsiranana Province, Northern Madagascar
Sapphires from Antsiranana Province, Northern Madagascar | Gems & Gemology

Since 1996, large quantities of yellow to blue sapphires have been recovered from alluvial deposits derived from basaltic rocks in northern Madagascar.

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Sapphire and Garnet from Kalalani, Tanga Province, Tanzania

Located just 3 km south of the famous Umba locality, the geologically similar Kalalani area hosts deposits of gem-quality sapphire.

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The Separation of Natural from Synthetic Colourless Sapphire

Greater amounts of colourless sapphire—promoted primarily as diamond substitutes, but also as natural gemstones—have been seen in the gem market during the past decade.

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Some Diagnostic Features of Russian Hydrothermal Synthetic Rubies and Sapphires

Most Russian hydrothermal synthetic rubies and pink, orange, green, blue and violet sapphires—coloured by chromium and/or nickel—reveal diagnostic zigzag or mosaic-like growth structures associated with colour zoning.

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Rubies and Fancy-Colour Sapphires from Nepal

Gem-quality rubies and fancy-colour sapphires have been recovered from dolomite marble lenses located high in the Himalayan mountains of east-central Nepal (Ganesh Himal).

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Sapphires from Southern Vietnam
Sapphires from Southern Vietnam

Gem-quality blue to bluish green sapphires from basaltic terrains in southern provinces of Vietnam have been entering the gemstone market since the late 1980s.

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Rubies and Fancy Sapphires from Vietnam
Rubies and Fancy Sapphires from Vietnam

Gem-quality rubies and pink to purple sapphires are being recovered from the Luc Yen and Quy Chau mining regions of Vietnam.

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