Rock Breaker is an early-game station that destroys stone-like blocks (like Cobblestone, Limestone, Meteorite Rock, etc.) and returns any useful materials that were hiding inside these rocks. Most blocks cost 0 pixels, and the materials within them can be very valuable, so this is very beneficial to do.
Rock Breaker processes 1 block every 0.75 seconds. Later in the game it gets replaced by Rock Crusher, which is faster and yields better results.
See the page Rock Crusher for the list of stones/rocks that can be crushed.
Sifter and Powder Sifter can process powder-like blocks in a similar manner.
Electronics (Electronics tree).