There is a terrain called Quarry in Graveyard Keeper. It can be found further to the west from the Forest near the River. If you unlock it, you will gain access to an unlimited source of stones, iron, marble and coal.
To get there, you first need to get through a closed passage. For that task you will need 2 wooden planks, 4 flitch and 4 nails.
There you will discover an abandoned shack, where you can build. You can create the same objects here like when near the "main" house.
Aside from that, here you can find stone, coal and iron deposits. From each one of those you will mine whole blocks of resources, instead of fragments. Those can be stored in iron ore stockpile or stone stockpile and broken into fragments.
To get to the marble deposit you need 7 flitch, 4 simple iron parts and 7 nails. Thanks to that you will gain access to marble, used in construction of new objects and upgrades.