There are several resources in Skyforge that have weekly limitations. Once the limitation is met, the resource will offer other items in it's place and will continue to do so until the cap is reset. All of the items are listed as "Valuables/Groups of Valuables". These include:
These resources reset every Tuesday at 9:00 PM PT (US) / every Wednesday at 05:00 AM GMT (EU) on logon or after a player portals to another zone. Also keep in mind that the Tatical Situation will need to update on the map before players can see the items/resources reset on the map.