Sulfate rocks are one of the problematic rocks that have always caused many problems during or after construction of infrastructures. In this research, by sampling of Gachsaran Formation sulfate rock layers outcrops at the four under construction, reservoir dam sites in Iran and performing lithological experiments, uniaxial compressive strength (UCS), ultrasonic tests, the relationship between the P-wave velocity and UCS of rocks with different mineral composition and the effect of rock texture on these properties were investigated in dry and saturated conditions. The results of this research confirmed that the studied sulfate rocks had P-wave velocities ranging from 4.5 to 5.5 km / s and ranged from “high” to “very high” class in Anon's (1979) P-wave classification. In gypsum-anhydrite rocks, by increasing anhydrite content, the P-wave and the UCS of the rock increase. In rocks composed of gypsum-clay minerals and clay sized carbonates, with increasing amount of recent minerals, although the UCS increases relatively, the P-wave velocity decreases. Although this study showed that there is a correlation between the mineral composition and the P-wave velocity in sulfate rocks, but this correlation does not lead to predictive equations with sufficient reliability.
