Yamanashi Crystal

A granite body extends from the Kofu Basin to Kawakami in Nagano Prefecture, and pegmatites are scattered through its higher parts around Mount Kinpu; quartz crystals grew in these pegmatites, in gas cavities near granite contacts and in hydrothermal veins. The Yamanashi Jewelry Museum describes the main localities: Otome Mine (various crystal forms, including Japan-law twins); Mount Hachiman (long, slightly yellowish prismatic crystals and Japan-law twins, with a single crystal said to be the largest in the East (Tōyō)); Takemori (crystals with tourmaline, muscovite and chlorite inclusions, formerly large and colourless); Suishō-tōge (green-included crystals); Mukaiyama (dark green and brown needle inclusions); and Kurobera (light brown to black smoky quartz with potassium feldspar, rarely amethyst). Meiji-era localities also included Kurasawayama, Oshidashiyama, Kawahake and Ichinose. Overmining reduced output by about 1889 and mining became impossible by the end of the Meiji era; Otome, which produced highly transparent colourless and white crystals, later worked tungsten and silica and closed in 1981.

Yamanashi crystal has the ordinary properties of quartz, so its origin cannot be proved from mineral properties alone. Kofu became a crystal-cutting centre, and imports of Brazilian rough quartz began in 1915, so crystal objects made or polished in Yamanashi are not necessarily of Yamanashi origin. A claim of Yamanashi origin therefore rests on provenance records rather than on testing.

Quartz arrowheads about 3,000–5,000 years old, from Jōmon-period dwellings in Makioka and Enzan, are regarded as the start of crystal working in Yamanashi, and crystal beads appear among Kofun-period grave goods. The Tamamoro Shrine in Enzan recorded a crystal as its sacred object, and the Kanazakura Shrine treasures crystal balls. Around 1834 Yasuke of the Kyoto bead-maker Tamaya is said to have taught crystal polishing to the Kanazakura Shrine priests; workshops spread to Kofu, a crystal ball was shown at the 1873 Vienna World's Fair, and in 1976 Koshu crystal and precious-stone carving (Kōshū suishō kiseki zaiku) was designated a national traditional craft. The industry grew into Japan's largest jewellery cluster, and University of Yamanashi research led to Japan's first industrial production of synthetic quartz.

In the Kinpusan area the discovery of crystal was bound up with the worship of water sources: crystal was believed to be a mass of water, and polished crystals became sacred treasures of the Kanazakura Shrine. Retailers such as Pascle repeat that crystal was once called "water spirit" (suisei) and was said to be ice made by the gods.