Ōya stone

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Rough blocks of Ōya stone
Surface, worked Ōya stone
Dismantling chamber as a museum

Ōya stone ( Japanese 大谷 石 , Ōya-ishi ) is a light- colored tuff that is found in the vicinity of the Japanese town of Ōya, now a district of Utsunomiya , and has been used for building houses since ancient times.

description

The rock was formed in the early Tertiary , when the Japanese islands were still largely underwater, by solidifying the ash from volcanic eruptions in the water. This rock is found exclusively in the vicinity of the district inya in an extension of 8 km east-west and 37 km north-south and at a depth of 200 to 300 m.

Because of its properties, its low density, good fire resistance and easy processing, the stone has been used for residential houses, warehouses, fire-resistant walls, trench fortifications, as floor slabs, for stone walls, gate posts, building cladding and the like. a. used. The stone is particularly common in Utsunomiya, with a third of all production going to the Kantō area.

Due to the increasing use of concrete, the demand - despite its good usability and good appearance - has decreased. Occasionally, however, a susceptibility to weathering can also be observed.

Dismantling

In order not to disrupt agriculture, the stone is mined underground, creating large caves, some of which were converted into army storage rooms in 1944. In 1979 a cave was opened to the public as a kind of museum. In 1989 an old cave collapsed in another place, creating a crater 100 m in diameter and 30 m deep. The area was then searched for abandoned and unmapped caves.

Originally the stone was mined by hand. A simple tool called “crane beak” ( tsuruhashi ) was used to detach blocks of the size 5 sun × 1 shaku × 3 shaku. One worker managed ten blocks a day in this way, and it was also difficult to bring the 70 kg blocks to the surface. - This was done until around 1960, but mechanical dismantling began as early as 1952. This allowed the yield to be increased to 50 blocks per worker and day.

Well-known examples of its use

literature

  • Tochigi-ken no rekishi sampo henshū iinkai (Ed.): Oya-ishi . In: Tochigi-ken no rekishi sampo. Yamakawa Shuppan, 2008. ISBN 978-4-634-24609-6 . P. 26.

Web links