The report documents the results of a limited number of static and dynamic tests on one tuff from the location of the Diamond Mine Event tunnel at the Nevada Test Site. The tests comprised the first experimental study conducted in the then newly developed dynamic high-pressure triaxial test device. The purpose of the study was to determine loading rate effects on the uniaxial strain, hydrostatic compression, and triaxial shear response of that tuff when loaded statically (approximately 2 minutes to peak stress) and dynamically (approximately 20 msec to peak stress). The results indicated that rate effects were of secondary importance when compared with the effects of variation of water content of specimens. Primary consideration should be given to testing the tuff at its in situ water content. (Author).