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Webster 1913 Edition

Noun.

[See

(Min.)

(a)

A mineral related to ottrelite.

(b)

Clay slate; argillaceous schist.

Noun.

[Gr. a leaf, and a stone.] A petrified leaf, or a mineral having the figure of a leaf.

phyllite ‎(plural phyllites)

(geology) a type of metamorphic rock formed from clay-rich sediments called pelites