Corundum

Field of view: 5 mm. Corundum associated with muscovite. The hexagonal platy blue crystals are corundum, and their cross sections are observed as lines. The opaque gray plates exhibiting perfect cleavage are muscovite, and the opaque white parts in the interstices are quartz. Muscovite always exists between corundum and quartz because quartz and corundum cannot co-exist under this formation condition.

Recovered from a pneumatolytic deposit associated with S-type (Ilmenite-series) granodiorite. Formed in the early Paleocene (63 Ma).

Corundum from this location was described in 1943.