Carnelian

Antiquity ran on wax and stone. A Roman letter was closed with a bead of hot wax and the press of a ring, and the stone in the ring, more often than any other, was carnelian. The preference was practical before it was anything else: sealing wax releases cleanly from polished carnelian. The seal lifted away crisp, and a carved oval of translucent red became a person’s working signature. Engravers cut each device in reverse so the wax would read true; the Metropolitan Museum keeps drawers of these ring stones, Greek and Roman, their portraits still sharp.

The habit proved durable. During the Egyptian campaign, Napoleon acquired an octagonal carnelian seal cut with an old inscription; Napoleon III prized it after him, and the Prince Imperial wore it until his death in 1879.

For centuries, carnelian was the stone of authorship, the material a hand reached for when something had to be signed. A dial is a quieter form of the same idea: a small red field, cut thin, marking time instead of consent.