The reliable method of synthesizing diamond at HPHT condition was first disclosed by GE, through Nature in 1955, with no information about the apparatus used nor actual method of conversion from graphite to diamond. No disclosure was kept continued till 1959, when patents and scientific journal papers describing the actual method were published at the same time.
We had to start the trial of developing a process for industrial production of diamond, under a difficult situation that the newly disclosed technical factors were completely covered with GE’s exclusive patent rights. On the other hand, some Japanese industries in that time had strong intention of challenge to realize new and their original attainment in technology and science, in the background of their regrowth from the depression after the war.
Thus, we could have opportunity of making rather basic or explorative search for new and original methods different from those of GE, and fortunately as a researcher, we could find a series of composite systems certainly catalyzing the diamond formation from graphite. Two types of cubic apparatuses were also newly designed with concept of excellent mechanical accuracy in repeated use together with easiness of operation. Some evaluation experiments finally resulted in the formation of large transparent and colorless particles of diamond (>0.5mm) without sensitive P-T control, in a wide range of P-T condition. Need of pressure of several kilobars higher than that with the process using the Ni-based alloy, was the remaining subject. Some condition could produce polycrystalline particles with nearly cubic shape and lightly greyish color, around 2mm in size, like naturally produced polycrystalline particles.
The author would like to show our experience for explaining the technical situation and the background of the age when we started, though the development activity itself might be improper in the current situation where risk of investment and early gain are severely considered.
Recently, synthetic diamonds are often found on the market in Japan. Among them, yellow diamond is often produced by the HPHT method (left of Fig.1), and colorless diamond is often produced by the CVD method (right of Fig.1). These diamonds have several inclusions. One inclusion consisted of metallic about Co and Fe2N. The price per 1 carat is tens of thousands of yen. These diamonds are said to be imported mainly via China and India. These synthetic diamonds have been sold as "lab-grown diamonds" in Japan.
Diamond emits characteristic fluorescence due to optical defects and impurities. Inspection using fluorescence is a very important item in gem identification, such as a method of visually observing fluorescence to ultraviolet light, fluorescence image analysis with DiamondViewTM, and measurement with an optical instrument. A natural pink diamond and a synthetic pink diamond show distinctive fluorescence. The wavelength distribution of the fluorescence was measured with a fluorescence spectrofluorometer. The excitation wavelength having the maximum fluorescence spectrum and the change in the fluorescence spectrum due to the fluctuation of the excitation wavelength was observed by measuring the 3D fluorescence spectrum.
A HPHT treated color typeⅡ a pink diamond with remarkable NV centers showed 498nm and 505nm photoluminescence（PL） peaks, which rarely appear in HPHT treated diamonds. Natural color typeⅡ a pink and brown diamonds were compared with the HPHT treated pink diamond here. Among 71 natural color pink and 100 brown diamonds, 4 pink and 36 brown diamonds showed both 498nm and 505nm peaks. Only 2 brown diamonds of them exhibited distinct NV peaks in PL spectra, but these peaks are weaker than the ones of the HPHT treated diamonds. Although 3 pink diamonds showed remarkable NV centers, both 498nm and 505nm peaks did not appear in them. Above 2 brown and 3 pink diamonds exhibited GR1, which was not present in the HPHT treated pink diamond.
Irradiated greenish blue CVD synthetic melee diamonds were found in similar colored irradiated natural melee diamonds. Several thousand greenish blue melee diamonds were tested in GIA Tokyo laboratory. Infrared absorption spectroscopy, photoluminescence spectroscopy, and DiamondView analysis revealed that most of them were irradiated natural melee diamonds and some of them were irradiated CVD synthetic melee diamonds. Infrared absorption spectra of all CVD synthetic melee diamonds tested in this report showed a peak at 3123 cm–1, while their photoluminescence spectra showed a doublet peak at 596/597 nm. Those peaks are specific to CVD synthetic diamonds without post-growth annealing. From these spectra, CVD synthetic melee diamonds found in this study were concluded to be irradiated without post-growth annealing.
We have studied the Marimo-like carbon growth with using the diamond-supported transition-metal catalysts in the hydrocarbon gas phase. The Marimo-like carbon consisted with carbon nanofilaments (CNFs) having the diamond support as a nuclei, i.e., this is a unique sp3-sp2 carbon composite material expected for wider applications.
“The blue carbuncle” in the novel of Sherlock Holmes series by Sir Arthur Conan Doyle has many coincidences with the Hope diamond in the description of that novel, and the high awareness of the Hope diamond at the time indicates that the Hope diamond could be a motif of “the blue carbuncle”.
Topaz is one of the common gemstone and known as the birth stone of November. It can divide into two type; OH-type and F type. In this study, we investigate chemical composition using LIBS, to measure directly H and F content. And we discus about relationship between OH or F contents and reflective indices.
We analyzed ruby and blue sapphire from Luc Yen, Vietnam and compared with ones from other localities. 3D-plot of V-Cr-Fe and logistic regression using trace elements show a good indicator to distinguish rubies from Vietnam and Myanmar. 3D-plot of V-Fe-Ga shows a good indicator to distinguish metamorphic origin blue sapphires which includes Vietnam.
Jadeite has been used as one of ornamental gem stones from olden times. Although jadeites going on the market are mainly from Myanmar at present, they also have been found from Guatemala, Japan, California, Kazakhstan and Russia. Some Russian jadeites have been studied based on geological and petrological approaches so far1, however their gemological features are still unclear. We had an opportunity to visit a closed jadeite mine at Voikar-Syninsky area, Polar Urals, in 2013. In this presentation, we report the gemological features of the jadeites. This closed mine was called “the Levoketchpel deposit” and was reportedly found in 19592. The mining activities at this area were not long because of the small-scale mining and the low quality of jadeite. The jadeites are observed as dikes within serpentinized peridotites. The jadeite samples are whitish, pale-green to vivid green and show a mottled color distribution. The samples show mosaic to aggregate structure and are mainly composed of jadeite grains with minor amounts of natrolite, feldspar, chromite and zircon. UV-Vis spectra suggest that the green color is produced by the presence of Cr3+ and Fe3+. Trace element concentrations of the jadeites are determined by LA-ICP-MS technique to discuss the differences with jadeites from other localities3,4.
Microscopic observation, chemical analysis and X-ray analysis were performed on the origin of fluorescence of Yooperlite. From this result, Yooperlite （Sodalite） appears to be formed by reacting Nepheline and NaCl.
Recent years, low purity precious metal accessory are commonly sold as low-carat gold and platinum bearing alloy, it contain large amount of base metal. It may cause metal allergies. We perform to analyze chemical composition of these alloys and detect the characteristic elements.
The sol-gel method of synthesizing silica glass from a liquid raw material is a simple experiment that can be performed at room temperature without heating. One experimental system can be used to give assignments for each student's goals. For example, simple operations such as reagent metering and mixing, comparison of catalysts, understanding of hydrolysis reaction and dehydration condensation reaction, understanding of light interference based on observation of play of color effect, yield from final product Calculation. It takes about two weeks before the synthesized silica glass precipitates and can be confirmed. This time, while trying to compare the products by catalysis in the experiment class, authors explained the play of color effect of gem opal and the structural color of insect wings.
Presently, in Japan the classification of gem corals is carried out by using advanced technology. Phylogenetic classification that analyzed the nucleotide sequence of mitochondrial gene and structural analysis of the tip in coral bone axis is also performed by trace elements in ICP-MS. This study examined the difference between red coral (Paracorallium japonicum) in the Japanese coastal waters and red coral (Corallium rubrum) in the Mediterranean. In particular, we focused on differences in hardness and magnification tests, and verified whether the comparison between the two could be used for discrimination. Among “Aka-sango”, those that show a certain deep red color are called "blood red corals" We also make reference to the range of color called "red coral" in this study.
Precious coral is a gemstone of which Japan is a major country of origin and exporter. Recent years their resource exhaustion is worried due to overfishing and poaching caused by the soaring price. One of the solutions of such issues is to establish scientific evidences of Japanese origin. Vielzeuf et al. (2018) reports that Mediterranean and Pacific precious corals are differentiated by Pb and Ba ratio using the chemistry analysis of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In this presentation, trace element chemistries using LA-ICP-MS of various Japanese precious corals from Kochi, Kagoshima, Okinawa and Nagasaki are compared with those from Mediterranean, Philippine and Midway precious corals, discussing with the possibility of origin identification.
High quality(esp“teri”) pearls have existed long before the method of pearl farming were established in Japan. The teri is related to crystal structure of nacreous layer. We study what pearls express rose-pink interference color with scanning electron microscope.
In the quality element of a pearl, the most important thing is a “Teri”. We study measuring method and measurement example of its “Teri.” And we measured some strands of pearls and considered the applicability to the grading.
There are several kind of forms about the exfoliation and the crack in nacreous layer called “spot” which are caused during processing. We study the difference of the structure and the development of degradation between some forms.