Handbook for the Appreciation of Gemstones

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Handbook for the Appreciation of Gemstones

Message par Tsubo » 15 Septembre 2022, 12:41

Handbook for the Appreciation of Japanese Traditional Crafts by the Japan Kōgei Association

The history of gemstone processing in East Asia has its origins in Zhou dynasty (1050-221 BC) China, where it was used in the making of burial accessories, and the tradition has continued up to the present day. Japan also has a long history of gemstone work dating back to early times, the techniques having been introduced to areas such as Izumo (present day Shimane Prefecture), which is rich in raw materials like agate, crystal and jasper. Numerous examples survive in the Shosoin Treasury. Gemstone work of this early period is found in the form of Buddhist artefacts and on dress accessories, musical instruments and mirrors. During the Heain period (794-1185), however, these traditions began to decline and by the Kamakura period (1185-1336) had been died out completely. There was then a revival in the form of gemstone polishing by hand when crystal ore was discovered near the foot of Mount Kongo in Yamanashi Prefecture at the end of the Edo period (1615-1868).
Information about the techniques used can be gleaned from works such as the Shokunin-zukushi-e (Illustrated Compendium of Artisanal Crafts). Increasing interest in the skills of gemstone processing during the Meiji period (1868-1912) stimulated the importation of various kinds of precious stone and the establishment of gemstone work as a recognised craft discipline. Today the area around Kofu in Yamanashi Prefecture produces more carved gemstones than anywhere else in the world.
Gemstones are broadly classified as either hardstones or softstones. The oldest examples of Japanese gemstone work are large hardstone beads from the Jomon period (10,500-300 BC), the materials most commonly used for beading being agate, jasper, crystal and amber. For carved work the favoured materials are jade, agate, white crystal, red crystal, green quartz, amethyst, tiger's eye, lapis lazuli, sodalite and malachite.
Once the material has been chosen and the design worked out, under-drawing is carried out on the surface of the stone. Work progresses gradually, the first step being to use carborundum to make small wedge-shaped cuts resembling a toothcomb along the lines of the under-drawing. The unwanted parts are then removed by grinding with carborundum and a rotating device fitted with a round iron tip (koma). Increasingly finer grades of carborundum are used as the shape takes form. Final polishing is carried out with chrome oxide and a rotating wooden tip.

Terms used

Shako = Giant clams from the seas around Taiwan and Okinawa and one of the shippo (Seven Jewels) in Buddhist terminology. Shako was highly prized as a decorative material.
Kujaku-ishi = Malachite, a mineral containing copper carbonate and copper hydroxide whose natural patterning is reminiscent of peacock feathers, has been used for decorative purposes and as a pigment since early times.