A rock similar to flint in its properties, but occurring in large masses, which flint does not. There is a rock the size of a house about haflway up the west bank of Moosehead Lake that the Indians traded as far away as Michigan, according to a plaque put up by the phone company.

Chert (?), n. [Ir. ceart stone, perh. akin to E. crag.] (Min.) An impure, massive, flintlike quartz or hornstone, of a dull color.

I didn't know before that the name is of Irish origin.