Three different types of crushing machines, impact, cone and jaw, are used to break large rocks into gravel and dirt. Most are used in the construction industry either to gather and break up raw ore at a quarry or to combine that rock with other materials to pave roadways.
Impact crushers pound on rocks until they pulverize. The large pieces go into the top of a cage-like container, which is where the impact shaft does its work. As the rock is pulverized, it falls through holes in the bottom of the container. Coal, limestone and gypsum are often broken up in impact crushers.
Cone crushers squeeze big rocks into little ones. The ore is placed into the top of the machine where it grinds against a constantly moving spindle with a mantle. The rock is squeezed between the mantle and the container section. Big pieces break off and fall into the next section, which breaks the rocks down further. Once pulverized, the small pieces fall through an opening on the bottom.
The jaw crusher is most often used at quarries. A backhoe operator dumps a load of large rocks into the top of the crusher. The rock falls between two vertical jaws, one fixed and the other constantly moving back and forth. The rock passes through several crushers before it falls through a hole in the bottom and onto a conveyor belt to be expelled.