This is a medium grey (basalt?) possible burnisher/polisher/smoother found at 2137.224 mASL, 4.00 m from the NW baulk and 2.3 m from the NE baulk. It has a notch at one end, amongst a number of scored lines, so it may have had a different function than burnishing, but it is difficult to say.
Retouch:
Patination: