The weathering classification used here in was prepared by Murphy (1985) for the US
Army Corps of Engineers (Fig. 1). This classification is simpler than most, and is more
easily adapted to field use than many other classifications. Murphy’s classification was
modified to include the sound and feel of the square end of a 3-lb rock hammer (a Nolan
hammer) hitting the rock. This is a personal classification and depends on many factors,
including the strength of the individual wielding the rock hammer, as well as the weight
of the hammer itself. In addition to the descriptions for each weathering grade shown in
Fig. 1, the modified classification includes the following: