X線透過法による宝石の鑑定
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概要
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Although X-ray transmission technique (X-radiography) has been utilized to identify some gemstones, such as natural and cultured pearls, or natural diamond and its synthetic imitation, no quantitative investigation has been done of this important technique. The amount of X-ray transmission is defined by average atomic number of compounds, intensity of X-ray source, duration of irradiation, and the thickness of specimens. The intensity and duration of X-ray irradiation can be set at a constant value, the thickness can be measured, and the average atomic numbers can be calculated based on the chemical compositions of the stones. It is possible, therefore, to make quantitative comparision of the amount of X-ray transmission, i. e. intensity of the stones on X-ray radiographs, from which gem identification can be made. Inten, sities (darkness) on X-radiographs taken under the same conditions versus thickness measurements of various gemstones have shown that a straight line can be drawn for each kind of gemstone, and that such lines have different inclinations depending on average atomic numbers, i,e. different gemstones. Gemstones with smaller atomic numbers such as diamond (average atomic number 6) show steeper inclinations (Fig. 5. 7. 8). Naturally, gemstones having similar average atomic numbers, e.g. corudum, spinel, jadeite (average atomic number 10) can not be identified by this technique. Intensitles on X-radiographs are measured by the Sakura intensity. meter PDA-81, which is a kind of photographic. exposure meters, on the image projected on the screen of a projector. Calibration of the intensity meter is made so as to meet the ptesent pdrpose (Fig. 1).
- 宝石学会(日本)の論文
- 1977-12-15