Rock Crusher Cone Used Fire Pit. Rock Crusher Bit For A Fire Pit cone crusher fire pit. how to build a cone rock crusher fire pit Jan 22, Cone pit biochar is simple, effective and cheap If your biomass is dry and you are still having trouble getting a strong fire, try building a top lit fire cones from a rock crusher to burn in the size of crusher cone i have gives details.Dec 10, 2013 River Rock- A fire pit with river rock is also a very nice and inviting look. This is also an easy DIY project. Design your shape, and create a concrete structure in the shape you want your pit (usually square or circle.) Place a fire bowl in the middle and fill in the shape with gravel.