Dumortierite

Nekoyama mine

Nagano, Manno city, Nakatado county, Kagawa pref., Japan

Field of view: 2 mm. Dumortierite associated with pyrophyllite. The massive dark blue part is dumortierite. The surrounding massive white host is aggregate of fine pyrophyllite crystals.

Recovered from a pyrophyllite deposit formed by pyrophyllitization alteration by andesite of granite and associated hornfels in a low-pressure regional metamorphic belt. Formed in the middle Miocene (13 Ma).

Other localities

List of Japanese dumortierite localities

Momura (Pyrophyllite, Fibrous)
Kyonosawa (Pyrophyllite, Massive)
Shima Mine (Pyrophyllite, Massive)
Nekoyama (Pyrophyllite, Massive)
Taromaru (High-T metamorphic, Fibrous)