By hitting Jacques and getting out of range, his gems won't spawn until you're back into range. That range happens to expand to a place that's on the front side of the mountain. By hitting him in a specific way to cause the Gems to autocollect in the lava (not easy), you can have the gems collect while you're off gallivanting in the rest of the level.
This doesn't have a particular use right now, because there are high-value gems at the vortex area. If a quick way to consistently get up to that vortex were discovered though, well, could be interesting huh?
