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Kauri gum is a fossilized resin detracted from kauri trees (''Agathis australis''), which is made into crafts such as jewellery. Kauri forests once covered much of the North Island of New Zealand, before Māori and European settlers caused deforestation, causing several areas to revert to sand dunes, scrubs, and swamps. The ancient kauri fields continued to provide a source for the gum and the remaining forests.〔Hayward, pp 4-5〕 Kauri gum formed when resin from a kauri trees leaked out through fractures or cracks in the bark, hardening with the exposure to air. Lumps commonly fell to the ground and became covered with soil and forest litter, eventually fossilising. Other lumps formed as branches forked or trees were damaged, which released the resin.〔Hayward, p 2〕 ==Uses== The Māori had many uses for the gum, which they called ''kapia''. Fresh gum was used as a type of chewing gum (older gum was softened by soaking and mixing with juice of the puha thistle). Highly flammable, the gum was also used as a fire-starter, or bound in flax to act as a torch. Burnt and mixed with animal fat, it made a dark pigment for ''moko'' tattooing.〔Hayward, p 3〕 Kauri gum was also crafted into jewellery, keepsakes, and small decorative items. Like amber, kauri gum sometimes includes insects and plant material. Kauri gum was used commercially in varnish, and can be considered a type of copal (the name given to resin used in such a way). Kauri gum was found to be particularly good for this, and from the mid-1840s was exported to London and America. Tentative exports had begun a few years earlier, however, for use in marine glue and as fire-kindlers;〔 gum had even made up part of an export cargo to Australia in 1814.〔 Since the kauri gum was found to mix more easily with linseed oil, at lower temperatures, than other resins, by the 1890s, 70 percent of all oil varnishes made in England used kauri gum.〔Hayward, p 45〕 It was used to a limited extent in paints during the late 19th century, and from 1910 was used extensively in the manufacture of linoleum. From the 1930s, the market for gum dropped as synthetic alternatives were found, but there remained niche uses for the gum in jewellery and specialist high-grade varnish for violins.〔 Kauri gum was Auckland's main export in the second half of the 19th century, sustaining much of the early growth of the city. Between 1850 and 1950, 450,000 tons of gum were exported. The peak in the gum market was 1899, with 11,116 tons exported that year, with a value of £600,000 ($989,700).〔Hayward, p 46〕〔Dunmore, p 21〕 The average annual export was over 5,000 tons, with the average price gained £63 ($103.91) per ton.〔Reed, p 114〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Kauri gum」の詳細全文を読む スポンサード リンク
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