One Hundred Years of Federal Mining Safety and Health Research

produced most of the national supply of metallic zirconium. This metal was used by the U.S.
Atomic Energy Commission in atomic power applications. Eventually this process was taken
over by private companies to produce zirconium metal in quantity [CRS 1976].
3.6 Mechanization of Coal Mining over the Course of the Century
Underground coal mining production methods evolved several times throughout the 20th
century. At the beginning of the century, traditional pick mining and blasting, with hand loading
of the broken coal, was the norm (see Figure 25). By 1930, undercutting machines had largely
replaced hand picks for undercutting and mechanical loading had greatly increased (see Figure
26). Conventional mining by drilling and blasting was gradually replaced by continuous miners
during the 50s and 60s, while longwall mining became a dominant coal mining production
method during the 70s and 80s (see Figure 27).
Figure 25. Undercutting coal with a hand pick in the early 20 th century.
27