[in Japanese]

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Most natural-color pink diamonds exhibit blue fluorescence when exposed to UV radiation. Orange fluorescence is commonly observed in irradiated and heat treated color pink diamonds, including CVD synthetic diamonds. AGT Gem Laboratory examined 18 natural-color pink diamonds with orange fluorescence in 2006-2015. IR absorption spectroscopy confirmed the pink diamonds were all type Ⅱa. The most characteristic feature was a broad 507nm band in the UV-Vis absorption spectra at room temperature. In addition, at liquid-nitrogen temperature 575nm and 637nm absorption by NV centers were observed, however, 595nm absorption was not detected.

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We had a chance to inspect 211 pieces of melee diamonds. According to the seller, R Company, these were CVD synthetic diamonds. Using FT-IR, we checked infrared spectroscopy of these diamonds. 12 pieces were clearly Type I and we concluded that they were natural. 199 pieces were defined as Type II and we kept inspection. As the result of more inspections such as Photoluminescence measurement, we concluded 198 pieces were synthetic diamonds made by HTHP. And one piece was natural even though it was Type II. For finding natural stones and no confirmation of CVD method, it was a strange package.

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In this study we examined 45 synthetic diamonds from a gemological point of view to find difference from natural stones. The melee-size diamonds were grown by HPHT method in the range between colorless to near-colorless, which were obtained from gem market and assumedly produced in China and polished in India. The number of the case in which HPHT synthetic diamonds in melee size were found to be set in jewelry is sharply rising recently. More active work is, therefore, necessary to identify the synthetic diamond for appropriate screening and disclosure of correct information in order to keep fair trading of gem diamond, although individual synthetic diamond can be identified by combining standard gem testing techniques and specific ones in gem testing laboratories.

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Indirect observation of light beams scattered by cut diamonds which are radiated with external straight light incident is partially available for estimation of their "cut grade". Numerical tendency of solid angle (Ω) for the scattered beams indicates "exponential distribution" which may be attributed to statically random division of straight illumination; it is also regarded as optical scattering by transparent polyhedral volume constructed by facets. And, while such qualitative universal rule is observed in smaller Ω region, deviation from "exponential rule" is also observed in larger Ω region and this deviation remarkably grows up with higher cut grade, such as "excellent grade". Both qualitative and quantitative discussion are required for consequence.

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Seoul Jewelry Industry Support Center(SJC) was established to invigorate the jewelry industry. The research team of SJC has performed analysis support and monitoring of jewelry. The analysis for jewelry is required for non-destructive method or similar method to minimize of destruction. LIBS analysis was useful as new application for gold quantification and identification of various gemstones as like diamond and colored stones.

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LIBS analysis method is famous for ore exploration, factory automated line analysis, and Mars exploration. Beryllium diffused corundum are already analyzed using LIBS equipment to date. In this study, we try to apply LIBS analysis for several gemstones and gem related materials.

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Discriminant analysis is a popular statistical method that can reduce the multiple dimensions of variables and provide reliable classification accuracy. In this study, we used LA-ICP-MS for trace element analysis of amethyst and found discriminant analysis with ⁷Li, ⁹Be, ¹¹B, ²³Na, ²⁷Al, ³⁹K, ⁴⁵Sc, ⁴⁷Ti, ⁶⁶Zn, ⁶⁹Ga, ⁷²Ge, ⁹⁰Zr and ²⁰⁸Pb is a good indicator for the identification of natural and synthetic amethyst.

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Oil inclusions in quartz from Afghanistan/-Pakistan and solid inclusions from Herkimer, NY were investigated using organic geochemical analysis. Samples from Afghanistan/-Pakistan included a large quantity of n-alkanes, but did not include sterane, triterpane or isoprenoid hydrocarbons. The distribution of n-alkanes was unimodal, with peak for C₁₁ or C₁₃. The carbon preference index (CPI) for n-alkanes was less than 1.0. Alkylbenzens are characteristic compounds that are fluorescent in the inclusion in quartz from Afghanistan/-Pakistan. Herkimer Diamond does not have inclusions exhibiting fluorescence. The inclusions in Herkimer Diamond quartz were solid graphite. Herkimer Diamond quartz was hosted by Paleozoic dolostone; this dolostone was used for organic geochemical analysis in this study. The biomarker compositions extracted from this dolostone were similar to the composition of oil quartz. There is a possibility that the environment of alkylbenzene formation is related to the origin of clean, clear quartz crystals.

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In 1980s, we have encountered several synthetic emeralds in the gem market in Japan. Kyocera (named Crescent Vert or Inamori stone), Seiko (named Bijoreve) and a few companies (non-named). We report non-named synthetic emerald. This emerald was made by flux method. R.I is 1.562-1.558. A Raman spectrum has clear bands at 653 and 1168 cm^-1.

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With the comparison of V₂O₅ content, some co-relationships with the strength of its colour are detected in heated samples, but not in un-heated ones. Also, we confirmed the colouring agent of so-called "fancy colour tanzanite" as pink colour is by manganese and green is by chromium. Also, on this year visit, the mining at block. D is very active and produces higher quality than block. B.

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Market trends in the Japanese gem trade will be discussed based on Gem Identification Report requests received by Central Gem Laboratory over a 5 year period.

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The blue opal from Akase, Komatsu-city, Ishikawa prefecture, Japan has unique feature of its blue colour. Unlike other Japanese opal, it has blue colour and the colour is not originated from trace elements which causes the absorption but from the Rayleigh scattering.

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We experimented how the pigment of the Black-Lipped Cultured pearl and its shell changed by bleaching with the method usually used for akoya pearls.

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Great green turban and abalone are used in the inlaid mother-of-pearl technique(Raden).In this study,we analyzed the structural characteristics of nacre in these shells for the method of identification between abalone and great green turban.

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"Teri" is the most important subject of all other elements in Akoya pearls. It is obvious that the strength of " Teri" depends on various factors such as water temperature and crystal structure.We reconsidered the previous reports and searched about the some method to produce the pearls with strong teri.

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