After looking it up a little bit, it seems like that's the stone Algus used to transform at the end of the Rabanastre dungeon. They most likely took it after the battle and are examining it. Let's hope that it's not a job crystal, you don't want to turn into a Lucavi!
You can remain optimistic about a gunblade job, I do recall there being interviews that said some new jobs may be unique to FFXIV. However, it's also fairly normal Garlean weaponry, perhaps hinting more that a Garlean NPC will become important than a new job being added.