Once you dig out all the sand, it will never respawn. You are guaranteed to have at least 100 sand tiles on a map (any map having less is rejected and regenerated).
Here are the minimum amounts of tiles for each level:
- Overworld:
- Rock: 100
- Sand: 100
- Grass: 100
- Tree: 100
- Stairs Down: 2
- Stairs Up: 2 (As determined by the Sky)
- Cave level -1:
- Rock: 100
- Dirt: 100
- Iron: 20
- Stairs Down: 2
- Stairs Up: 2 (As determined by the Overworld)
- Cave level -2:
- Rock: 100
- Dirt: 100
- Gold: 20
- Stairs Down: 2
- Stairs Up: 2 (As determined by the Cave Level -1)
- Cave level -3:
- Rock: 100
- Dirt: 100
- Gem: 20
- Stairs Up: 2 (As determined by the Overworld)
- Sky
- Cloud: 2000
- Stairs Down: 2