Hidaka Jade

Hidaka jade was found in the Penke-yukutorashinai stream, a tributary of the Chiroro River at Chisaka, Hidaka Town. It occurs in rodingite derived from serpentinite, along the boundary between serpentinite and rodingite, where chromium from the chromian spinel-bearing serpentinite was taken up into new minerals. The material was actively mined and sold as jewelry in the late 1960s to the 1980s (Showa 40s–50s), but the deposit appears to have been exhausted within about three years of its discovery.

Mineralogically Hidaka jade is chromian diopside, not jadeite (the mineral of jadeite jade) and not the amphibole of nephrite, so it falls outside the strict definition of jade; it is better described as a chromian diopside rock. Polished pieces typically show dark green uvarovite spots, black chromian spinel spots and white pectolite or wollastonite areas in the green diopside.

In 1964 Kubouchi Kan'ichi of Hakodate, convinced that the green rocks of the Hidaka Mountains must include jade, asked Murakami Akira of Hidaka to search for it; in 1966 a jade-like stone was found at Chisaka and reported in the Hokkaido Shimbun as a nephrite discovery. Bamba Takeo of the Geological Survey of Japan's Hokkaido branch then showed that it was chromian diopside, and in 1980 described it in the Journal of the Gemmological Society of Japan under the title "Chrome-diopside jade from Chisaka, Hokkaido", which gained it recognition as a gem.