The Gem-A editorial team are excited to launch the latest issue of The Journal of Gemmology, Volume 36, No. 2, keeping the Gem-A community updated with the latest in gemmological research.
Features in the Spotlight
Focusing on Blue Zircon from Ratanakiri, Cambodia, authors Manuela Zeug, Lutz Nasdala, Bhuwadol Wanthanachaisaeng, Walter A. Balmer, Fernando Corfu and Manfred Wilder share their recent research exploring the colouration of Ratanakiri zircon, which is well known for its vivid blue colour under heat treatment.
These zircon samples from Ratanakiri (0.3-5.1g) include two untreated brown crystals and three blue specimens that were heat treated at ~1000°C under reducing conditions for a few hours.
Photo by M. Zeug.
The actual cause of Ratanakiri zircon's colouration is still under debate: while the untreated brown material turns blue under reducing conditions (~900-1000°C) the specimens analysed in this paper demonstrate that the heat treatment does not result in detectable changes in the zircon's structural state. Here, Zeug et al, offer their data to help address this ongoing debate.
More Feature Articles
In our other feature articles, Shi Tang and his team discuss their analysis of a thick overgrowth of CVD synthetic diamond on a natural diamond that was identified at the Beijing laboratory of the National Gemstone Testing Centre (NGTC) in October 2017.
Distribution of CVD synthetic diamond overgrowth on a natural diamond, discussed by Tang et al.
Elsewhere, Emmanuel Fritsch FGA and Aurélien Delaunay explore the characteristics of Chameleon Diamonds, with an example of an 'Atypical 25.85 ct Stone', while SSEF's Laurent Cartier FGA and Michael Krzemnicki FGA, together with Bertalan Lendvay and Joana Meyer, review the use of DNA fingerprinting on pearls, coral and ivory in gemmology.
Biogenic gem materials suitable for DNA testing include items such as these from the SSEF and H.A. Hänni collections:
cultured pearls and associated shell material (P. maxima and P. margaritifera ~15cm tall), corals (including Corallium rubrum branches up to ~ 10cm tall) and ivory (warthog and mammoth).
Photo by Vito Lanzafame, SSEF.
Stay Updated with Gem Notes
This issue also returns with our regular installments on the latest technology and equipment in our 'What's New' section, together with a round-up of the latest on gemstone analysis in 'Gem Notes'.
Make sure you don't this issue's 'Conferences', which features reports on the 15th Annual Sinkankas Symposium on Tanzanite and Tsavorite, and the 76th Swiss Gemmological Society Annual Conference.
READ MORE: Gems and Jewellery Summer 2018 Has Arrived
Gem-A members are kept up-to-date with the latest events and conferences in the gemmological calendar in our 'Gem-A Notices' and 'Learning Opportunities' section, while 'New Media' and 'Literature of Interest' keeps you fully informed on the latest gemmological publications.
So, Gem-A members look out for your copies of the Journal of Gemmology Vol 36.2, which are on their way to you now! Alternatively you can log in to access your online copy. ■
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In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.
If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world.
Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.
Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.
Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.
Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...
Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.
Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.
The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!