The schmidt hammer,weathering and rock surface roughness

Measures of the differential relief of adjacent feldspar and pyroxene grains provide the first clear negative correlation of Schmidt hammer rebound (R-) values and degree of weathering. However, weathering and roughness are intimately related, so the latter cannot be seen simply as a source of error limiting the utility of the Schmidt hammer. Only where surfaces had similar textures prior to weathering can R-values be compared directly. Even where surface texture is well controlled, differences in R-values should be viewed critically rather than assigned indiscriminately to differences in degree of weathering.