Tailings is a waste stream produced by mining industry. It is often stored on the surface in a retaining structure, called tailing impoundment surrounded by tailing dams. Strength property of tailings is important for safety of tailings dam construction. In this study, direct simple shear tests were performed on two Swedish tailings from Malmberget mine and Svappaavare mine in Northern Sweden. The apparatus used is NGI direct simple shear apparatus. The estimated maximal friction angle from shear tests ranged from 15.9 to 24.3°, with cohesions from 0‐16.3 kPa. One phenomenon noticed was that for tailings the sample height started decrease after dilatancy. In order to know whether this is a material property, or it is due to the defect of the simple shear apparatus, a series of shear tests were done on Kalix sand. The result showed that this phenomenon happened also to the densely compacted sand, though more rarely. The decreased sample height after reaching the peak values is assumed to be related to both particle breakage and the deficiency of the shear apparatus.