The stonecutter goes from the storehouse to his mason (only one worker per mason), and from there to the nearest quarry (stone deposit).
It doesn't matter if several masons are nearby, they can all go to the same quarry (even if only one worker is shown cutting the stones).
Click on the mason to see the green little dots with flags. They will show you the worker's exact path, showing which quarry he is working at.
The more masons you have around one quarry, and the higher level those masons are, the faster the quarry will become exhausted.
When that happens, your stonecutters will be going to the next quarry, once again the nearest one still having stones left to be quarried.
If there are no quarries available that at that point haven't been exhausted,
then your stonecutters will stop working and their masons will get the exlamation mark saying they lack resources.
As soon as you've ordered your explorer to refind those now exhausted quarry, each stonecutter will once again find the nearest quarry.