A rectangular stone knife from Eastern Concord, MA

There are three arrowhead hunting seasons: in the spring, after they plow and it rains; in the fall after the harvest is brought in and it rains; and after the winter when the snow melts. The arrowhead I found a few weeks ago was from the winter season but the spring season just started, so I went out to see what was visible - at a place I go. I got lucky.The material is a mottled rhyolite formed with chunks of striated gray material in a matrix of black material with some smaller white crystals. In the first picture, some rust stains near the top of the rectangle suggest hafting. I wonder if it is the same as the material in this point from a few weekends ago (click here) which I found in the same place.