Rock is utilized as a construction medium in five broad categories: (1) underground openings or structures, (2) open cuts and excavations, (3) load-bearing surfaces, (4) as a dimensioned or structural component, and (5) as crushed mineral aggregate or stone. Due to man’s originally limited means of excavating and cutting, rock has been historically used primarily as a structural component. The ancients could attack rock with only their own manpower, furthered later by gunpowder and harnessed steam. Modern man is now served by a wide variety of rock excavating and cutting machines employing petroleum products, air, electricity, jet flame, and laser beams. These kinds of energy, along with improved explosives, have vastly improved and expanded the use of rock as a construction medium. The use of both underground space and the removal of rock as an obstruction is now largely a matter of economics only.