Here are some slate points, up to bayonet size, from the Maritime Archaic of Maine. 35cm=~14" long. Also, other Late Archaic cultures in the Northeast utilized ground slate weaponry, and the stems were often notched as mjm mentioned.
Example shown from RI showing notched stem.....
Hope you snag a complete bayonet some day, mjm. But you'll be hard pressed to top the point in your avatar!