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Bang Rak, Thailand

Saeseaw S.,Colored Stones | Sangsawong S.,GIA
Gems and Gemology | Year: 2014

Until now, the observation of three-phase inclusions in emeralds has been considered a potential indicator of Colombian origin. Nevertheless, emeralds from Afghanistan (Panjshir Valley), China (Davdar), and Zambia (Kafubu and a new deposit at Musakashi) may contain three-phase inclusions resembling those often found in specimens from Colombian deposits (Muzo, Chivor, La Pita, Coscuez, and Peñas Blancas). This article presents detailed photomicrographs of samples from these localities, with a focus on their multiphase inclusions. Also investigated are spectroscopic features and trace-element data. For the gemologist studying the origin of emeralds hosting three-phase inclusions, a powerful set of tools to aid in this determination comes from the combination of detailed microscopic examination, UV-Vis-NIR and FTIR spectroscopy, and LA-ICP-MS trace-element analysis. © 2014 Gemological Institute of America. Source


Giuliani G.,British Petroleum | Fallick A.E.,Isotope Geosciences Unit | Feneyrol J.,British Petroleum | Ohnenstetter D.,British Petroleum | And 2 more authors.
Mineralium Deposita | Year: 2011

The combination of oxygen isotope composition with V-Cr-Mn trace element concentrations of V-bearing garnets (tsavorites) originating from the main deposits of the Neoproterozoic Mozambique Metamorphic Belt is reported for the first time. The database enables the identification of the geological and geographical sources of the main productive areas from northern and southern Tanzania, Kenya, and Madagascar. Three consistent sets of δ18O values between 9. 5‰ and 11. 0‰, 11. 6‰ and 14. 5‰, and 15. 5‰ and 21. 1‰ have been recognized for primary deposits hosted in graphitic gneisses related to the Neoproterozic metasedimentary series. The δ18O value of tsavorite is a good tracer of the environment of its formation; the δ18O of the fluid in equilibrium with tsavorite was buffered by the host rock during metamorphism and fluid-rock interaction. This study is a first step in characterizing the geochemistry of gem tsavorite from most of the deposits and occurrences worldwide. © 2011 Springer-Verlag. Source


Shigley J.E.,GIA
Gems and Gemology | Year: 2013

It has been more than two decades since diamond ages have proven to be up to billions of years older than their host magmas of kimberlite or lamproite. Since then, there have been significant advances in the analysis of diamonds and their mineral inclusions, in the understanding of diamond-forming fluids in the mantle, and in the relationship of diamonds to the deep geology of the continents and the convecting mantle. The occurrence of natural diamonds is remarkable and important to earth studies. This article reviews current thinking of where, how, when, and why natural diamonds form. © 2013 Gemological Institute of America. Source


Gomez-Marlasca F.,GIA | Ghenzi N.,GIA | Stoliar P.,GIA | Stoliar P.,National University of San Martin of Argentina | And 5 more authors.
Applied Physics Letters | Year: 2011

We present a pulsing protocol that significantly increases the endurance of a titanium-manganite interface used as a binary memory cell. The core of this protocol is an algorithm that searches for the proper values for the set and reset pulses, canceling the drift in the resistance values. A set of experiments show the drift-free operation for more than 10 5 switching cycles, as well as the detrimental effect by changing the amplitude of pulses indicated by the protocol. We reproduced the results with a numerical model, which provides information on the dynamics of the oxygen vacancies during the switching cycles. © 2011 American Institute of Physics. Source


Ghenzi N.,GIA | Sanchez M.J.,Bariloche Atomic Center | Gomez-Marlasca F.,GIA | Levy P.,GIA | Rozenberg M.J.,University Paris - Sud
Journal of Applied Physics | Year: 2010

Multilevel resistance states in silver-manganite interfaces are studied both experimentally and through a realistic model that includes as a main ingredient the oxygen vacancies diffusion under applied electric fields. The switching threshold and amplitude studied through hysteresis switching loops are found to depend critically on the initial state. The associated vacancy profiles further unveil the prominent role of the effective electric field acting at the interfaces. While experimental results validate main assumptions of the model, the simulations allow to disentangle the microscopic mechanisms behind the resistive switching in metal-transition metal oxide interfaces. © 2010 American Institute of Physics. Source

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