An artifact visibility field indicating the typical size of material present on soil surfaces in addition to artifacts. Values measured on a sliding size scale from boulder (>300 mm) to cobble (300-75 mm) to coarse gravel (75-19 mm) to fine gravel (<19 mm) to sand (<5 mm). Possible values include “Boulder,” “Cobble,” “CoarseGravel,” “FineGravel,” and “Sand,” as well as ranges for units where walkers checked more than one box: “Boulder-Cobble,” “Boulder-Gravel,” “Cobble-Gravel,” and “Gravel-Sand. Units lacking data altogether list values as “Unrecorded.”