Kuji amber

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Kuji amber ( Japanese 久 慈 琥珀 , Kuji kohaku ) is the name of a type of amber from the largest amber discovery site in Japan near Kuji in the north of the main island of Honshū . In general, amber has been found in Japan in numerous locations from Hokkaidō in the north to Kyūshū in the south of the country over a distance of approximately 1800 km.

Occurrence, age, characteristics

The best-known and most abundant discovery area of ​​Japanese amber is located around 500 km north of Tokyo near Kuji. The oldest amber-bearing sediments in this area come from the Aptian (100 million years old), but most of them come from the Upper Cretaceous (approx. 80 million years old). The youngest are Miocene in age (approx. 30 million years). Due to the inclined layering of the sediments in the mountains near Kuji, the sites of this amber of very different ages are sometimes very close to one another. The amber occurs in carbonaceous and sandy sediments.

The Kuji amber appears in a variety of color nuances. Most of the pieces are orange and slightly cloudy. Many pieces have agate-like banding. The banding results from an alternation of strips of clear resin with strips in which there are numerous small bubbles. Cracks filled with quartz can be observed in some pieces . When the amber is heated to temperatures around 330 ° C, these bubbles burst. This creates a scent reminiscent of camphor .

History, extraction, use, trade

Kuji amber has been mined and processed in Japan for centuries. The extraction and trade of this amber can be traced back to the fifth century AD on the basis of grave goods. The transport of 1296 kg of amber from Kuji to Kyoto is documented for 1703 . At the same time, the city of Edo (now Tokyo) received significant amounts of amber from Kuji.

More recent amber mining is also only known from Kuji. Records from the mining operations show that daily production from a single mine in the area was up to 50 kg in the 1930s. Extrapolated to the twenty active mines at the time, this results in a (theoretical) annual production of up to 350 tons.

The largest known pieces of amber ever found in Japan also come from this area. Pieces weighing up to 60 kg are said to have been found at the beginning of the 20th century. Such large pieces from this period have not survived. One of the largest preserved pieces is in the Tokyo National Museum . It is a broken piece found in 1941 with a total weight of 16 kg. A specimen that was excavated in 1927 and weighed 19.875 kg is kept in a private collection. The amber mines around Kuji were badly damaged in World War II and industrial-scale mining was not resumed in the post-war period. Today only very few finds are made.

Kuji amber was used in jewelry until the outbreak of World War II. The Japanese Makie Urushi technique was also used here. After the industrial mining of amber at Kuji was stopped, artisans who had previously devoted themselves to amber processed tortoiseshell using their traditional techniques . With the entry into force of the Washington Convention on Endangered Species in 1973, this material was no longer available. At that time, Baltic amber was already being imported. Baltic amber is easier to work with than Kuji amber, which is often brittle and prone to cracking. The old techniques were retained even after the switch to Baltic amber. Contemporary amber objects in traditional Japanese craftsmanship are almost exclusively made from Baltic amber.

The only amber museum in Japan is located in Kuji.

Amber from other sites

None of the numerous amber finds in Japan can be compared with that of Kuji in terms of output. The amounts found in the following areas range from a few kilograms to a few hundredweight:

  • Area of Choshi , east of Tokyo. The amber finds from this area are from the Lower Cretaceous. Age (Lower Aptium, approx. 110 million years).
  • Iwaki, about 200 km north of Tokyo. The amber found here resembles the Kuji amber of the same age from the Cretaceous period.
  • Hokkaidō: Small amounts of amber of the Eocene age (approx. 40 million years) were and are found in coal mines.
  • In the extreme southwest of Honshū, near Ube , amber was found in the Upper Ocee layers.
  • Other sites on the main Japanese island of Honshū provided amber from Upper Miocene (up to 15 million years old) and Pliocene (less than 5 million years old) as well as copal .
  • Several amber finds are reported from the northern part of the South Island Kyushu.

Organic inclusions

Organic inclusions have been discovered in amber almost everywhere in Japan. However, the enclosed plants and animals are often very poorly preserved because amber was exposed to considerable tectonic stress in the course of its genesis . Earthquakes and the effects of heat have not only influenced the properties of the fossil resin in such a way that its artisanal processing is made more difficult, but also significantly damaged the inclusions.

literature

  • Dieter Schlee: The Bernstein Cabinet. Stuttgart Contributions to Natural History, Series C, Issue 28, Stuttgart 1990.
  • Kazuhisa Sasaki: Japanese Amber. In: Exhibition catalog Japanese Amber, Ed. Kaliningrad Amber Museum, Kaliningrad 2006.

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