The effect of mineralogy on slake durability of 36 mudrock samples was investigated. Samples were obtained from six different sites with distinct lithologies that included 12 mudstones from two sites, 14 mudshales from two sites, 6 clayshale and 4 siltstones. Slake durability tests were continued to fifth cycle to study the effect of different cycles on durability of mudrocks. The highest value of slake durability was measured for siltshale and the lowest for clayshale. The slake durability results of this study also indicate that there is no single parameter that can be used to predict the durability of mudrocks. The results show that durability is closely related to the quantity of clay minerals. Therefore, it can be concluded that variation in durability within mudrocks is controlled predominantly by mineralogy. A decrease in the slake durability was associated with an increase in clay content. It seems that other geological parameters such as fabric and weathering also affect the durability of mudrocks.

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