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Update: November 12, 2018

Yamanashi and Crystal

The geology of Yamanashi Prefecture includes widely distributed bands of igneous rock formed by cooling magma. Among them, granite, which is found in plutonic rock formed by slowly cooling magma, is common in the area from the Kofu Basin to Kawakami-mura in Nagano Prefecture. Deposits of pegmatite, an igneous rock containing exceptionally large crystals, are found in those granite masses at relatively high elevations, mainly in the area around Mt. Kinpu.

Crystals are frequently found in the pegmatites that occur in granite and are also common in hydrothermal veins. Pegmatites, the final product of the long, slow cooling of granite magma deep in the earth, are a source of large, high-quality crystals.

Granite is also the heat source for hydrothermal veins, and druse cavities or geodes (rock cavities formed when gas is trapped inside granite) are formed at the boundaries between different types of granite or near contact areas around them. As the granite cools, the trapped gas and fluids crystalize, forming rock crystals.


Otome produces a variety of rock crystals, including Japanese twin quartz crystals.


Hachimanyama produces the Far East’s largest hexagonal columnar mono-crystals and beautiful Japanese twin quartz crystals. Many long, slightly yellowish transparent crystals are found there.


Takemori produces crystals such as tourmaline, muscovite, and turquoise. In the past, it produced large, colorless, transparent crystals.


Suishotoge is known for green grass quartz and green semi-transparent crystals. Ghost crystals and chlorite crystals are also found there. This site produces crystal clusters renowned for their beautiful shine.


Mukouyama is known for crystals with dark green and brown leaf-shaped inclusions and transparent or semitransparent grass quartz crystals. It also produces Go stones and rock crystal clusters from large quartz veins.


Kurobera’s pegmatite geodes produce a wide variety of crystal clusters, from light brown and darker smokey quartz to potassium feldspar. Frequently curved lines appear in their columns. Sometimes, albeit rarely, amethysts are found.

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