In this study, the effect of calcium carbonate on triaxial compression strength, uni-axial compression strength (UCS), indirect tensile strength (sigma(t)) and slake durability index (I-d) were investigated. Additionally, according to triaxial compression strength tests results were investigated on the effect of calcium carbonate for Mohr-Coulornb (c, phi) and Hoek-Brown (sigma(ci), m(i)) failure criterion parameters. For this purpose, experimental studies have been carried out on core samples taken from blocks of marl formation in two different lignite basins which is a major open pit mine in Turkey. The results of experimental studies were analyzed statistically. Clay and carbonate content of marl is one of the main factors controlling the engineering properties of marl. Finally, the high compression strength and high slake durability index value especially for Soma district samples have been develop to its clay and carbonate minerals compositions.