Yoroi-iwa Stone Dike

Near the summit of a mountain in the center of Shiraishi-jima Island called “Onigajo” is a dike formed of aplite (fine-grained igneous rock) with granite piercing through. Its name “Yoroi-iwa” means “armor stone.” and it looks like a sleeve of armor worn by a giant. This armor-like pattern appears stretched over the face of the granite and contains small crevices and grooves, much like the surface of a Go" board. A rare and strangely-shaped rock formation, the country has designated it as a Natural Monument. It is divided into two, with the upper section 2.4 m wide and 1.8 m high, and the lower section 3 m wide and 8.2 m high.