They are unlocked at experience level 34.
They are stored in the barn.
Getting stone blocks
A sure way to get a stone block is to buy it with 10 dia.
Stone blocks can also sometimes be found in roadside shops for 1 to 342 coin per unit.
Finally, stone blocks can be randomly obtained when players:
- open mystery boxes and mystery packages
- spin the Wheel of Fortune
- fully satisfy a town visitor
- win prizes in derbies
- use mystery nets in the fishing lake
- watch a Night at the Movies trailer