カソード・ルミネッセンス法とその宝石学への応用 : 新しい鑑別法 Chthodoluminescence Method and it's Applications to Gemmology

本論文はカソード・ルミネッセンス(CL)法の宝石学への応用について述べている。CL法は宝石内部に残された様々なタイプの不均一を可視化する事ができる。これらの不均一は宝石の成長履歴に起因しているので、これからその宝石の成長過程を推定することができる。宝石の成長過程は個々の宝石によって異なるので、個々の宝石を識別(個体識別)することも可能となる。ここで取り上げた例はダイヤモンドとエメラルドであるが、詳細についてはそれぞれ宝石学会誌Vol.17,Vol.18を参照されたい。またダイヤモンドについては個体識別を容易にするためのCL像の画像処理法についても提案している。

Cathodoluminescence methods, both scanning electron microscope type and optical microscope type, have been applied to diamond and emeralds as representative examples of gemstones, with a hope of applying the method in daily gemmological identification works to distinguish natural from synthetic gemstones, and to fingerprinting a stone. Observations on growth banding revealed by CL images of diamond have demonstrated that (1) growth morphology of natural diamonds consists of flat {111} faces with or without curved {100} faces, whereas that of synthetic diamonds consist of flat {111} and {100} faces, and (2) each diamond has its characteristic pattern of growth banding. These characteristics can be used as diagnostic features to be used in discriminating natural and synthetic diamonds as well as finger-printing an individual stone. CL observations on ten pieces of synthetic emerald, which were identified beforehand by ordinary gemmological testing and NlR spectrum, have demonstrated that flux-grown emeralds show straight parallel growth bandings or "aurora-like" bright spots, whereas hydrothermally-grown emeralds show "comet-like" spots arranged in certain directions or show unique rhombic pattern. So, natural and synthetic emeralds can be distinguished by CL method moreover for synthetic one, growth method can be identified.