Protolithionite

Field of view: 10 mm. A group of protolithionite. The micaceous grayish-green crystals exhibiting perfect cleavage are protolithionite. Protolithionite is solid solution between siderophyllite and lepidolite, and present approved name is Li-bearing siderophyllite. The translucent white part at the lower right is gangue quartz. The dark gray part at the upper left is granite, host of the deposit.

Recovered from a pneumatolytic deposit formed near the boundary between welded tuff and S-type (Ilmenite-series) granite, members of a caldera complex. Formed in the Late Cretaceous (70 Ma).

Protolithionite from this location was described in 1979.