Shifty Shafts is an old mine north of the lake at the center of the Fortnite Chapter 3 map. If you get a Quest telling you to harvest stone there, we suggest you get straight to it for some pretty easy XP. Depending on the bus’ flight path, you should be able to land right on it, if not very close by.
Before you start harvesting stone, scan the area for weapons, and for other players attempting the same quest. You might need to defend yourself, so it’s always good to have a weapon. Now, not everything that looks like stone can be harvested for stone. You’re looking for tall outcrops and boulders, some of which are fairly small, others of which are found in large clusters. You might think that there’d be a lot of material inside the mine itself, but that’s not the case (although there should be at least one Chest down there). The stone is all on the surface, and not necessarily within the boundaries of the mine site, so make sure you look outside the fence, but don’t stray all the way out of the Shifty Shafts area.
Outcrops and small boulders yield about 40-50 stone, while the boulder clusters will get you about double that. How many you’ll need to smash will depend on your Quest target, but we managed to get 300 stone in one match in the space of just a few minutes.