The speaker is walking across rough, broken ground and looking closely at it. The title plays on "gray matter," which can mean brain as well as stone, and the poem moves between the two. The surface is crumbling "piece / meal," and what was gray sand now glitters under lichen. At night the same ground looks like the moon, alive with crickets and "dense with ambiguities," as if the landscape were something to be read and interpreted.
The comparisons to weathered wood and grimy old snow suggest slow decay, a kind of aging in place. The speaker seems to share in this, getting lost "in a maze of cracks." Then comes a wry line about taking a "micro dose of humility," which sounds like a small, sudden reminder of how little we matter against geological time. The humming power line at the end, buzzing with "ghosts of power," adds an eerie note. The mood is quiet, curious, and a little humbled, with some dry humor running through it.