These are rock (lithic) fragments
from the 1-2-mm grain-size fraction of the Apollo 16 regolith. The Apollo
16 mission landed in the feldspathic highlands, so there are few, if any,
mare basalts here. The rocks are mainly crystalline impact melt breccias,
regolith breccias, fragmental breccias, and a few pieces of largely unbrecciated
anorthosite (the white fragments). Click on image for enlargement.