Boron Rocks are quite a rare resource in the game and can be quite hard to get to and find.
For every 100 Boron Rocks you refine, you get 1 Boron Block back. To refine rocks, you need them to be in a warehouse.
Here is a list of the location where Boron Rocks can be found :
Boron BlockEditBoron Blocks are the result of 100 refined Boron Rocks.