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Chichibu Mine

Otaki, Chichibu city, Saitama pref., Japan


Field of view: 100 mm. Hedenbergite vein traversing crystalline limestone. The massive dark green part at the center is aggregate of fine hedenbergite and andradite. The dark green prisms at the both sides are hedenbergite, and the hedenbergite prisms are vertical to the vein. The opaque pale brown parts exhibiting perfect cleavage at the outside of the hedenbergite zone are kutonahorite. The black grains in kutonahorite are ilvaite. The white grains exhibiting perfect cleavage at the both sides end are calcite.

Recovered from a hedenbergite vein in a moderately low-temperature hydrothermal deposit combined with skarn formed by contact metamorphism of I-type (magnetite-series) quartz diorite. Formed in the late Miocene (6 Ma).

Hedenbergite from this location was described in 1903.


Field of view: 10 mm. Hedenbergite associated with albite. The tabular dark green crystals are hedenbergite. The opaque white crystals are albite. Recovered from a pocket of I-type (Magnetite-series) quartz diorite. Formed in the Late Miocene (6 Ma).

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