The Sharpners Pond diorite is a large, calc-alkaline, intermediate pluton in the Nashoba Terrane. It is early Silurian in age, and is composed mostly of hornblende diorite and a variety of tonalites. Although broadly inhomogeneous, this outcrop is exceptional with deformed breccia and possibly pillows of mafic, probably dioritic rock in with pinkish granodiorite or granite.
These are the two end member rock types: pinkish-gray granite and dark-gray mafic rock. Here the mafic rock appears to have some kind of foliation, which is may be truncated against the granite. If you stare long enough you may be able to convince yourself that the foliation in the mafic rock extends into the granite.
On this face there appear to be mafic breccia blocks enveloped by the pinkish granitic rock. Careful examination shows that the mafic rocks are not all alike; some are coarser, some are darker.
This image was taken from around the corner from the image immediately above, which here would be immediately to the right. On this face the breccia does not look particularly deformed, and many of the breccia blocks look remarkably like the pillows seen at Stop 3. In this image the inhomogeneity of the mafic and felsic rocks can be seen. Some of the felsic rock is pink or white, and some grades into an intermediate gray, suggestive of contamination of the felsic rock by the mafic.
These joint surfaces nicely expose a deformed mass of breccia blocks and/or pillows. Notice again the diversity of shades of gray of the mafic blocks.
This image is rather undistinguished, but it does show coarse granitic rock between fine-grained mafic blocks that mostly look like a breccia.