• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.317-322
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• 2002

We have studied the sawing sach as the round brilliant cut, cushion barion cut and marquise cut. Through this study, we could examined the rate of waste from the grinding work, and find a solution for many problems which could be derived from the grinding work. We could reduce the rate of waste by this study about sawing technique; 2.5 % for round brilliant cut, 2.5 % for cushion barion cut and 5.5 % for marquise cut.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.173-179
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• 2013

Even though a rough diamond shape is irregular and rugged, it is easy to be processed to make gem, shaped facets (table, crown, pavilion and girdle) were precisely treated because they influence on the evaluation of diamond grading. Those specifications suitable for the standard round brilliant cut diamond polishing were investigated and in 95 % statistical confidence interval, standard deviation, mean and acceptable tolerance were examined. According to these variables (size, angle, depth, and thickness) distribution, the frequency analysis of ratings and proportions were compared with each other. The correlation between each variables and the evidence of influence represented in proportion were determined by the regression analysis applying LSM (Least Square Method). In this research, it was recognized that table sizes of the diamond jewels and pavilion depth (in %) influence the rating decision and in particular, the depth of pavilion acting as the main factor of proportions, also plays an important role in optical phenomena.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.5
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• pp.205-210
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• 2003

Alexandrite-like cubic zirconia single crystals were grown by skull melting method. The R.F. generator (output power is 35 ㎾) used for skull melting was operated at 2 MHz. The grown crystals were doped with up to 1 or 1.5 wt% and 0.5 or 1 wt% of rare earth metal ion (Pr, Nd) on$ ZrO_2-Y_2O_3$ (12 mol%). The grown crystals were cut for slice (0.25 mm) and round brilliant (12 mm in diameter). The cut stones were heat treated in air and nitrogen at $1000^{\circ}C$ for 2 hours and their optical absorption spectra ($\lambda$ = 400∼700 nm) data were obtained.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.1
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• pp.35-40
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• 2007

Cobalt ($Co^{2+}$) doped yttria stabilized cubic zirconia (YSZ, $Y_2O_3\;:\;25{\sim}50wt%$) single crystals grown by a skull melting method were heat-treated in $N_2\;at\;1000^{\circ}C$ for 5 hrs. The reddish brown single crystals were changed into either violet or blue color, respectively. Before and after heat treatment, the Co-doped YSZ crystals cut for wafers (${\phi}6.5{\times}t\;2mm$) and round brilliant (${\phi}10mm$). The optical and structural properties were examined by UV-VIS spectrophotometer and XRD. These results are analyzed absorption by $Co^{2+}\;(^4A_2(^4F)\to{^4P})\;and\;Co^{3+}$, change of energy gap and lattice parameter.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.3
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• pp.105-109
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• 2011

Critical angle of quartz (R.I. ${\fallingdotseq}$ 1.553) and diamond (R.I. = 2.417) are $40.09^{\circ}$ and $24.26^{\circ}$ that calculated by $sin{\theta}=r_2/r_1$ (r = refractive index, $r_1$ > $r_2$). Brilliance of quartz and diamond are 20.33% and 55.07%. The brilliance data are result of study on the incident light internal round brilliant cut quartz and diamond by the critical angle. Cause of bow-tie phenomenon can be studied by application of critical angle theory and light path inside fancy shape brilliant cut. When refractormetry with typical gem refractometer, critical angle of quartz and corundum are $59.1^{\circ}$ and $77.9^{\circ}$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.4
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• pp.159-163
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• 2010

Co-(0.5 mol%) and Ce-(0~0.3 mol%) doped cubic zirconia ($ZrO_2:Y_2O_3$=64:36 mol%) single crystals grown by a skull melting method were heat-treated in $N_2$ at $1200^{\circ}C$ for 3 hrs. The brown-colored as-grown single crystals were changed into either green or blue color after the heat treatment. Before and after the heat treatment, the YSZ (yttriastabilized zirconia) single crystals were cut for wafer form (${\phi}7mm{\times}t2mm$) and round brilliant cut ($\phi$ 12 mm). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by $Ce^{3+}(^2F_{5/2},\;_{7/2}(4f){\rightarrow}^2T_g(5d^1)),\;Co^{2+}(^4A_2(^4F){\rightarrow}^4T_1(^4F)$ or $^4T_1(^4P))$ and $Co^{3+}$, change of ionization energy and lattice parameter were confirmed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.105-109
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• 2004

In this study, we analyzed the influences of appraising elements such as weight, color and clarity of natural diamonds on their value in the round brilliant cut diamonds. To analyze the influences of these elements on the value of diamonds, data were made from a Rapaport Diamond Report which is the most reliable source of diamond prices. As the result of this study, it is clearly understood that color and clarity equally influenced the value of diamonds as a whole, but there were some partial variations according to grades of both elements. That is, value of clarity was higher than that of color in higher-quality diamonds but value of clarity was lower than that of color in lower-quality diamonds. Also, value of diamonds were closely co-related by three main elements which were weight, color and clarity, but weight was the most influencing element on the value of natural diamonds.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.1
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• pp.21-26
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• 2020

This article reports the result on the spectroscopic analysis of the three Lightbox CVD-grown diamonds. Lightbox Jewelry, a De Beers company, has begun selling CVD laboratory-grown diamonds since September 2018. Recently, we had the opportunity to examine three Lightbox's pendant necklaces. The 0.25 ct, 0.25 ct, and 0.26 ct round brilliant were graded as "H" near colorless, Fancy Vivid orangy pink, and Fancy Vivid blue with cut grades of excellent, respectively. The laser-inscribed Lightbox logo under the table, large enough to be easily visible with a microscope. Based on the spectroscopic techniques, for near colorless sample was not subjected to post-growth HPHT processing to improve its color. For pink sample, optical centers at H3, 3H, 594 nm, NV, and GR1 were recorded. It was speculated that the pink sample have been received irradiation and annealing. In addition, the blue CVD synthetic sample was concluded to be irradiated without annealing.