Opus Signinum

opus signinum, in mosaic, type of simple, unpatterned or roughly patterned pavement commonly used in Roman times. It was composed of river gravel, small pieces of stone, or terra-cotta fragments cemented in lime or clay.

Opus signinum was the prevalent form of pavement in Roman houses from the 1st century bc to about the 2nd century ad. It was rapidly superseded in main rooms by patterned pavement mosaics made up of small, shaped pieces of stone, ceramic, or glass tesserae.