What Bōshū stone is
Bōshū stone, bōshū-ishi, is a tuffaceous building stone quarried around Mount Nokogiri in the south of the Boso Peninsula, Chiba Prefecture, on the boundary of Futtsu and Kyonan. It is also named after the villages where it was cut, such as Kanaya stone or Motona stone. The mountain has long been known as a source of stone, and the sheer faces of its old quarries still stand; quarrying ended in the later Showa period.
Soft enough to work easily and resistant to fire, it was used for foundations, retaining walls, boundary walls, storehouses and kitchen ranges. In the former village of Kanaya at the foot of the mountain, storehouses, walls and fences of Bōshū stone shape the streetscape. It is said to have been shipped to Edo and later Tokyo, and in the modern era to have been used for harbour works.
Quality varied within the stone. The record for the stone storehouse of the Suzuki family says it was built of carefully laid sakurame stone, regarded as the finest grade of Bōshū stone, which suggests that masons graded the stone by its texture.
Reading the records and the stone
The Suzuki family house in Kanaya, Futtsu, preserves a group of buildings and structures made with the stone. The main house uses local Bōshū stone for its foundations and bathroom, the stone storehouse is a two-storey hipped building laid entirely in it, and the retaining wall along the front is built of cut blocks 0.3 metres high and 0.8 metres long laid six or seven courses high to 1.8 metres, in level courses with continuous horizontal joints. The same stone serves as a building component, as the structure of a building and as the boundary of the property.
For the pattern of laying, compare Nunozumi, stone laid in level courses, and Ranzumi, irregular stones laid without courses. The record's term seisōzumi refers to coursed work with level horizontal joints.
On site, look at the weathering. Bōshū stone is said to weather readily, and storehouses and walls built of it often show crumbling surfaces and chipped corners and lower courses. The record, rather than appearance, is the reliable basis for identifying the source.
References
- 鈴木家住宅石蔵｜国指定文化財等データベース（文化庁）
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00007973
- 鈴木家住宅石垣｜国指定文化財等データベース（文化庁）
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00007976
- 鈴木家住宅主屋｜国指定文化財等データベース（文化庁）
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00007972
- 鋸山 日本寺（地獄のぞき）｜まるごと e! ちば（千葉県観光物産協会）
- https://maruchiba.jp/spot/index_1_2____0__地獄のぞき___.html
Last verified: 2026.09.26