“... Sado (Sado-ga-shima or Sado-shima) is an island, at the western coast of Honshu, located about 60 km northwest of Niigata City in the sea of Japan. .. The landscape is marked by volcanism.

The island is known due to its gold mines, which have been exploited since 1601 by Japanese prisoners, mostly politically unwelcome persons ...they were in operation until 1989, most recently by the company Mitsubishi.

In the southern part of the island in a quarry huge blocks of yellow, red and yellow, but also red Jasper, which is occasionally traversed by quartz veins, were found. This quarry is to be no longer active. You will find waterworn Jasper-specimen probably also in rivers and on the beach. The material is offered  in many stores under the name "Akadama ishi" (red ball stone), presented ... in dome-shaped specimen on a wooden base. The prices are high, especially for cut and polished material, because for 30-40 years no new material was found )...

A dealer offered in the Internet these Jaspers, under http://akadamaisi.web.fc2.com/setumei.htm, but the site is entirely in Japanese. Anyway, it gives a good impression of  the findings (and the prices!)

The Mineralogical literature of Japan, especially the older, neglected the quartz varieties such as agate and jasper unfortunately, so that you can find just a few notes and background information for such collecting-sites..."

according to personal communication with Jörg Liebe, Sankt Ingbert