Identifying quern and grinding stones
Saddle querns, rotary querns, and the daily grind made literal.
Querns ground grain for millennia. The saddle quern (Neolithic to Iron Age) is a dished lower stone worn smooth by a rubbing stone. The rotary quern (Iron Age onward) is a pair of thick discs — the upper with a central hopper hole and a handle socket, the lower with a central spindle hole.
Fragments are the usual find: an arc of thick stone with one worn, often striated face and a drilled hole edge. Materials were chosen for grit — lava querns from famous continental sources were imported in quantity in Roman and medieval times, and their vesicular grey fabric is distinctive.
Estimate the original diameter from the fragment's curve, note thickness, stone type, and which faces show wear. Querns rarely strayed far from home — a quern fragment is strong evidence of nearby settlement, so the findspot deserves care.