Yep, it's on Saturday the 25, listed as the Fredericksburg Indian Artifact Show. Been there many times, well worth the trip. I think it's the second largest show in Tx. Plenty of mighty fine artifacts.
The "Gem, Mineral & fossil show " at FredB is Sat - Sun 18 & 19. Google the show will put you on the Rockhounds website.
Traditionally a few dealers at a GMF show will offer a few select artifacts along with a mixture of other items.
The Pure " artifact show " at FredB is Sat the 25th only. As Te says, the best in Tx after Temple.