3 . Structural terms including fault rock terms

Many of the definitions given below were adopted by the SCMR without difficulty; others gave rise to considerable debate. Problems arose for a variety of reasons, namely: the variable usage of terms across the geological community (e.g. gneiss and schist); terms such as slate and cleavage proved difficult because there are no similar terms in many non-English speaking countries; equally, the difference between cleavage and schistosity and the use of texture and microstructure proved major sticking points. In other cases it was difficult to differentiate between rock types solely on features observable in the field at hand-specimen scale or in thin section examination as required by the SCMR scheme (Schmid et al., this vol.). Also, although the SCMR scheme seeks to avoid terms based on processes wherever possible, this was not practical with many terms related to fault rocks (e.g. mylonite and cataclasite).