gems, corundum, treatments.6, HPHT

For decades now heat treatment has been used successfully as an enhancement process for sapphires, particularly blue sapphires, and is both accepted and widely practiced in the jewellery industry. Considered one of the classic coloured gemstones, fine quality blue sapphire is always in great demand. The techniques used for heat treatment are constantly being developed, not only in Thailand, and seem to involve increasingly sophisticated instruments. For instance, the famous Sri Lankan heat treatment technique known as the “Punsiri method” that has been seen to improve the colour of blue sapphire from various deposits successfully (G. DuToit et al., 2009). In 2013, a Korean company successfully developed a new technique for enhancing blue sapphire and began to trade their product in the gem market. This process involves the intentional application of pressure while heating the stone. This new technique significantly reduces the time needed to change the stone’s colour and/or clarity compared with the traditional heat treatment where stones are simply heated in a furnace. So far, Sri Lankan sapphire, (the so called Geuda sapphires) is the only commercial product that this company claims to be treating successfully. The blue sapphire resulting from this treatment commonly shows a typical strong OH-related absorption in the Mid-IR spectrum. This and some characteristic inclusion features are important keys for identification of sapphire that has undergone heat and pressure treatment. Further study is required to increase our understanding of the change mechanism and also the exact role of pressure in this process.

gems, corundum, Ethiopia.12, sapphire

At the 2017 Tucson Gem Show, author Andrew Lucas was approached by Ethiopian dealers a ending a seminar given by Shane McClure, Global Director, Colored Stone Svc. They proposed to Lucas and McClure to conduct research on Ethiopian gemstone deposits for GIA. This led to correspondence between Lucas and Teweldbrhan Abay, Director of the Mineral Marke ng and Value Chain Directorate over the next several months to coordinate a joint project between GIA and the Ethiopian Ministry of Mines Petroleum and Natural Gas (MOMPNG).

gems, corundum, gemology, gemmology,

Lovely book on gemology, illustrated largely by the stunning photographs of the late Tino Hammid, along with others from the renowned Jeff Scovil. Volume 1 covers the science of gemmology, including the chemical nature of gemstones, their physical and optical properties, basic crystallography, the absorption of light, the spectroscope, polarized light, the polariscope, pleochroism, the dichroscope, colour filters, specific gravity, luminescence, magnification, thermal conductivity, imitation, assembled and lab-created gemstones, gemstone treatments and enhancements, mining, diamond and coloured gemstone cutting and coloured gemstone and diamond grading. Volume 2 covers the identification of gemstones based on their colour and transparency, ‘Reflections’ consisting of 134 pages of photographs that capture the true beauty and incredible talent of award winning gem cutter John Dyer, and GEMFACTS that focuses on the seventeen most common gem species and varieties.

gems, corundum, Synthetic corundum.7, flux ruby, Douros flux ruby

Extremely detailed discussion of the history and gemology of the Douros flux-grown synthetic ruby.

gems, Chinese jewelry, jade, jadeite, fei cui, nephrite, coral, amber, sapphire, tourmaline

This illustrated volume examines treasures formerly associated with Puyi (1906–1967), the last emperor of the Qing dynasty, that became dispersed following the collapse of the imperial household and the political upheavals of the twentieth century. Drawing on surviving objects and historical documentation, the catalogue traces the fate of items removed or separated from the former imperial collections and presents examples of jewelry, jade, precious objects, works of art, and other possessions connected with Puyi and the Qing court. The objects provide evidence of late imperial collecting, craftsmanship, court taste, and material culture while also illuminating the complicated dispersal of the imperial collections through removal, sale, loss, and changing ownership. Richly illustrated, the book serves both as a record of surviving scattered treasures and as a study of their relationship to Puyi and the final decades of China’s imperial tradition.

gems, corundum, Kashmir sapphire, India.12, fashioning.9

Sometimes you can guess that a sapphire comes from Kashmir just with a glance at its specific cut. This cut is typical of old European standards and was developed in the beginning of the 20th century. When mining started in Kashmir, Europe had been famous for a while for its lapidary know-how, especially thanks to the invention of corundum jewel-lined pivot in the Jura region. As a consequence, a lot of rough stones were sent to Europe to be cut under the control of Mr Modiano, a friend of the Maharaja of Kashmir.. A Kashmir sapphire generally gets cut in a cushion shape, with a brilliant cut on the crown and a step cut on the pavilion. The culet is faceted as well. What differentiates this sapphire from the others? Under a microscope, white zones will often be observed, and those are renowned for giving the crystal its famous silky aspect. Stone cutters specially chose to cut big and flat facets on the pavilion because of this cloudy appearance, so that more light gets into the crystal. The main objective of the crown’s brilliant cut is to emphasize the fire coming from the pavilion’s big facets. Some sapphires from other regions than Kashmir have the same kind of cloudy crystallization and can be cut in the same way, in order to be confused with the real Kashmir material. This cut is usually never used in big sapphires cutting centers, such as Sri Lanka, Myanmar and Madagascar.

gems, corundum, USA.12, Montana.12, sapphire, melt inclusions

We report here compositions of glassy melt inclusions hosted in sapphires (gem quality corundum) from three alluvial deposits in Montana, USA including the Rock Creek, Dry Cottonwood Creek, and Missouri River deposits. While it is likely that sapphires in these deposits were transported to the surface by Eocene age volcanic events, their ultimate origin is still controversial with many models suggesting the sapphires are xenocrysts with a metamorphic or metasomatic genesis. Melt inclusions are trachytic, dacitic, and rhyolitic in composition. Microscopic observations allow separation between primary and secondary melt inclusions. The primary melt inclusions represent the silicate liquid that was present at the time of sapphire formation and are enriched in volatile components (8–14wt.%). Secondary melt inclusions analyzed here for Dry Cottonwood Creek and Rock Creek sapphires are relatively volatile depleted and represent the magma that carried the sapphires to the surface. We propose that alluvial Montana sapphires from these deposits formed through a peritectic melting reaction during partial melting of a hydrated plagioclase-rich protolith (e.g. an anorthosite). The heat needed to drive this reaction was likely derived from the intrusion of mantle-derived mafic magmas near the base of the continental lithosphere during rollback of the Farallon slab around 50Ma. These mafic magmas may have ended up as the ultimate carrier of the sapphires to the surface as evidenced by the French Bar trachybasalt near the Missouri River deposit. Alternatively, the trachytic, rhyolitic, and dacitic secondary melt inclusions at Rock Creek and Dry Cottonwood Creek suggests that the same magmas produced during the partial melting event that generated the sapphires may have also transported them to the surface. Determining the genesis of these deposits will further our understanding of sapphire deposits around the world and may help guide future sapphire prospecting techniques. This work is also important to help reveal the history of mantle-derived mafic magmas as they pass through the continental crust.

gems, jewelry, diamond, history of jewelry, emerald, pearl, ruby, topaz, imperial topaz, Brazil, amethyst, glyptic

Joao Távora Magalhães, Sotheby’s: The story of this book—and of the exhibition that first accompanied it in Lisbon—began with a chance visit to S.J. Phillips on New Bond Street in October 2016. Drawn in by an intriguing Instagram post, I stepped into this legendary gallery hoping to see some fine jewels. What I found, quietly displayed in the back room, was a remarkable group of pieces whose color and energy were both astonishing and deeply familiar to my Portuguese eyes. In that moment, I knew this extraordinary collection had to be brought to Lisbon for public display. A quick conversation with Francis, Jonathan, and Nicolas Norton, the partners at S.J. Phillips, and a visit from our ever-supportive Chairman of Sotheby’s Asia, Patti Wong, set everything in motion. Portugal, in the context of European arts, has made an indelible mark by absorbing global influences from the many territories with which it has long been associated, creating a distinctively national style that found its finest expression in the Decorative Arts. The S.J. Phillips Collection of Portuguese jewels—centered on 18th-century masterpieces—perfectly embodies a moment of immense richness in Portuguese art, when Lisbon was receiving vast quantities of gold, diamonds, and minerals from Brazil. There, these treasures merged with the latest European artistic trends under the patronage of the great King Dom João V. Diana Scarisbrick, the foremost authority on historic jewelry, not only documents this pivotal period but also traces the development of this sophisticated art form in its entirety. Through her words and insights, we hope to bring greater international recognition to Portuguese jewels. Sotheby’s and S.J. Phillips have been neighbors on Bond Street—the heart of the art and antiques world—for a century, enjoying a warm, fruitful, and always mutually enriching relationship. It is a deep pleasure to mark this centennial friendship with this book. On a personal note, I offer my heartfelt thanks and admiration to Francis, Jonathan, and Nicolas Norton for assembling this exquisite collection and for allowing Sotheby’s and me to share in its story.

corundum, inclusions.5, Burma.12, gems

gems, corundum, Burma.12, ruby, sapphire, spinel, Mogok, Mong Hsu, jade, jadeite, fei cui, amber, peridot, diamond

The aim of this chapter is to review the locations, mineralogy and briefly the origins of the major gem deposits in Myanmar. Myanmar is fortunate in containing world-class gem deposits, such as the finest pigeon's-blood-coloured ruby from the Mogok Stone Tract in Mandalay Division, the Mong Hsu ruby deposit in Shan State and imperial coloured jadeite jade from Kachin State (Fig. 23.1). For the purposes of description the gemstone deposits in Myanmar are classified into: (1) primary hard-rock deposits in which the gemstones are hosted in the rocks in which they were crystallized or in their weathered products; and (2) secondary deposits in which the gemstones have been weathered out of their original (primary) host rock, transported and deposited as placer deposits in alluvial sediments. Examples of the primary-type gems are ruby in marble (Mogok, Mong Hsu and Sagyin), sapphire in syenite pegmatite, syenite and nepheline syenite (Mogok) and jadeite in serpentinized peridotite (Tawmaw). Other precious gemstones from primary deposits include spinel in marble (Mogok), peridot in dunite/peridotite (Mogok), topaz, aquamarine, tourmaline, quartz, etc. in pegmatite (Mogok, Mong Hsu and Momeik) and kyanite in quartzite (Moehnyin). Rare gemstones are often found in primary gem deposits in the Mogok Stone Tract and include johachidolite and hackmanite from pegmatites, painite from leucogranite and skarn, pollucite, petalite, phenakite, pezzottaite, monazite, danburite, jeremejevite and hambergite from pegmatites in the Momeik area.