Recently black pearls have been successfully cultivated in the Ishigaki Islands, Okinawa, and also in Tahiti Islands. Blue pearls have also been obtained occassionally among ordinary cultivated pearls. These have already appeared in the market. On the other hand, artificial colouring of pearls to obtain black and blue pearls has been performed and the products have been in the market since 1930. It has therefore become an urgent need to establish non-destructive methods to differentiate between true and artificially coloured black and blue pearls. To achieve this purpose, both true and artificially coloured black and blue pearls are investigated by means of (1) observation of fluorescence under ultraviolet light, (2) observaton under the polarization microscope, (3) investigation of different colouring on infrared film, (4) X-ray fluorescence analysis (black pearls), and (5) fiberscopic observation (blue pearls). It was found that true and artificially coloured black pearls may be easily distinguished by either a combination of four different methods or simply by comparing different colouringi on infrared films, but in the case of blue pearls, further studies are necessary. The definition of black and blue colors, origin of the colours, the methods of cultivation of black pearls are also described in some details.

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Fujiwara no Munetada 藤原宗忠 (1062-1141), who held the title of Udaijin 右大臣 during the years of the rule by ritired emperor Shirakawa-in 白河院, is well known for his diary, Chuyuki 『中右記』, a basic historical source for the period. However, Munetada also kept in his possession two family commentaries on the ceremony for the appointment and promotion of officials, the Joi Shidai and Jimoku Shidai 毎汨譽・恂汨譽. The Jimoku Shidai has been quoted in the Heian period work on the ceremony, Nakayama Naifu-sho ?R内府抄 which listed it as the Nakamikado Ufu-sho ?莓蜑E府抄; and during the Kamakura period the original was kept by the Kujo 九条 family and called the Nakamikado Ufu Jimoku-sho (Akaki-jiku) ?莓蜑E府除目抄・赤木軸. A Kamakura period copy of the Jimoku Shidai was placed by the Hirohashi 広橋 family into the care of Shimonogo Kyosai-kai 下郷共済会 in Shiga prefecture, which has preserved it to this day. While missing some chapters, this copy, according to a notation at the end of the text, was prepared in 1299 by Sangi Nakamikado no Munefuyu 中御門宗冬, the sixth generation grandson of Munetada. The manuscript used for this purpose was passed down from Munetada to his son Muneyoshi 宗能, then to the latter's son Muneie 宗家 ; and finally ended up in the archives of the Kujo family. The content of the jimoku Shidai consists of an explanation of the ritual order during the three days of official appointments and promotions in the spring, particulars for similar ceremonies held for capital officials (kyokan-jimoku 京官除目) and in extraordinary situations (rinji-jimoku 臨時除目), and finally a general summary of the whole ritual. The text has also been richly annotated with personal opinions, doubtful points and precedents set by former participants. Personages appearing in the work include Fujiwara no Tadazane 藤原忠実, Oe no Masafusa 大江匡房 and Minamoto no Toshifusa 源俊房. During the Nanboku-cho period, the Jimoku Shidai was quoted in the ceremonial writings, the Gyorogu-sho and Gyorogu-betsuroku 『魚魯愚抄』・『魚魯愚別録』, which listed it as Munetoshi-kyo-sho and Soseki-sho @俊卿抄E@赤抄 Munetoshi is of course Gondainagon Fujiwara no Munetoshi 権大納言藤原宗俊, the father of Munetada, which indicates that the main text may have been of his authorship. The fact that it was circulated as Munetada's Jimoku Shidai probably stems from the many annotations added by Munetada himself.

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