Precious metals are traded over-the-counter (OTC) and therefore are not subject to any "official" trading times.
Since the markets are worldwide, spot precious metals are traded almost around the clock.

The availability of Spot Metal Prices is Sundays 6:00 PM EST (market opening in Tokyo) to Fridays 4:30 PM EST (market close in New York).

Unavailable Monday to Thursday 5:15 PM to 6:00 PM EST (All markets closed).