Kyaw Moe

• Research Associate at Gemological Institute of America, New York

Strong photoluminescence (PL) of ND1 radiation center with zero-phonon line (ZPL) at 393.5 nm has been excited in irradiated diamonds with a laser working at a wavelength of 355 nm. Emission of the ND1 center consists of ZPL and vibrational replicas related to quasilocal vibrations of an energy 76 meV. PL and absorption spectra of ND1 center exhibi...

Detailed study of the luminescence of multiple brown CVD diamonds was performed. It has been found that the well-known optical center with zero-phonon line at 468 nm is a characteristic of brown color. It has been found that the defects responsible for 468 nm center are located within brown striations suggesting close relation of the 468 nm center...

Single crystal CVD diamond has been grown on (100)-oriented CVD diamond seed in six layers to a total thickness of 4.3 mm, each layer being grown in gas with increasing concentration of nitrogen. The nitrogen doping efficiency, distribution of color and internal stress have been studied by SIMS, optical absorption, Raman spectroscopy and birefringe...

Defect transformations in type Ib synthetic diamond annealed at a temperature of 1870 °C under stabilizing pressure (HPHT annealing) and in hydrogen atmosphere at normal pressure (LPHT annealing) are compared. Spectroscopic data obtained on the samples before and after annealing prove that the processes of nitrogen aggregation and formation of nitr...

Nitrogen-doped CVD diamond treated with electron irradiation and subsequent annealing at temperatures from 860 to 1900 °C was studied using fluorescence imaging, optical absorption and photoluminescence. It was found that nitrogen impurity produces many optical centers active throughout the infrared and visible spectral ranges. The most prominent o...

Microdiamonds ∼200 μm in size, occurring in ophiolitic chromitites and peridotites, have been reported in recent years. Owing to their unusual geological formation, there are several debates about their origin. We studied 30 microdiamonds from 3 sources: (1) chromitite ore in Luobusa, Tibet; (2) peridotite in Luobusa, Tibet; and (3) chromitite ore...

Detailed measurements of photoluminescence of commercial CVD diamond irradiated with 1 MeV commercial electron accelerator have been performed. It has been assumed that the depth distribution of radiation-induced defects can be described by contributions of two mechanisms: strong defect production by primary fast electrons and weak secondary irradi...

Full text available: https://www.gia.edu/gems-gemology/winter-2016-microworld-ferropericlase-inclusion-diamond

Photoluminescence and absorption properties of commercial brownish yellow nitrogen-doped gem quality CVD diamonds have been characterized using imaging and spectroscopic techniques. The measurements have been performed on the diamonds in as-received state and after treatment with electron irradiation and high temperature (LPHT) annealing. It is fou...

_____________________________________________________________________________________________ Ophiolites in Tibet and Russia are known to contain abundant microdiamonds [1,2]. Due to their unusual setting in the oceanic lithosphere rather than the cratonic lithosphere, as well as their small size and unaggregated nitrogen (C centres), many research...

Cultured pearls from Pinctada margaritifera can exhibit a broad range of natural bodycolors, including various pistachio-like colors ranging from greenish yellow to yellowish green. Bead-cultured pearls from P. margaritifera, treated by Ballerina Pearl Co. and possessing intense pistachio colors, have entered the market. Similar to Ballerina's "cho...

The green coloration of natural diamonds typically results from exposure to natural irradiation. This creates the GR1 optical center and in many diamonds, surficial damage, principally due to alpha radiation, which helps verify natural origin. In this study, 13 naturally irradiated diamonds with pronounced radiation stains were stepwise annealed fr...

The Russian company New Diamond Technology is producing colorless and near-colorless HPHTgrown synthetic diamonds for the gem trade. Forty-four faceted samples synthesized using modified cubic presses were analyzed using a combination of spectroscopic and gemological techniques to characterize the quality of the material and determine the means of...

The Russian company New Diamond Technology is producing colorless and near-colorless HPHT-grown synthetic diamonds for the gem trade. Forty-four faceted samples synthesized using modified cubic presses were analyzed using a combination of spectroscopic and gemological techniques to characterize the quality of the material and determine the means of...

The gemological and spectroscopic properties of 52 colorless to fancy light-colored HPHT synthetic diamonds (40 of them colorless or near-colorless) produced by AOTC using either toroid- or BARS-press technologies were characterized. In addition to achieving excellent color grades, these commercially available faceted synthetics had a weight range...

Gemological and spectroscopic properties of CVD synthetic diamonds from Gemesis Corp. were examined. Their color (colorless, near-colorless, and faint, ranging from F to L) and clarity (typically VVS) grades were comparable to those of top natural diamonds, and their average weight was nearly 0.5 ct. Absorption spectra in the mid- and near-infrared...

Gemological and spectroscopic properties of 43 CVD synthetic diamonds from Apollo Diamond Inc. were examined to characterize the latest generation of their CVD products. These samples, which included both faceted gems and partially polished crystals, were provided as representative examples of Apollo's 2006-2007 production. Relative to the Apollo C...

A large "Persian" turquoise cabochon was impregnated with a material that was also present in cavities on its base. Raman spectroscopy identified the filler as a UV-hardened polymer. Although such polymers have been seen as fillers in other gems, especially emerald, this is the first time the GIA Laboratory has seen turquoise treated with this mate...