Several types of instabilities can menace the personnel and equipment in the open cast mines. Their kinematicis dependent commonly on the nature, the structure, the fracturing and the strength of the rock mass. A scientific assessment vis-a-vis their equilibrium is suggested. For this task a considerable amount of field work must already carrying out to supply the necessary data ie: geometric, mecanic and geologic parameters. The main purpose of this research is identifying different modes of slope failures that may develop on the career “ENOF” of Jebel Gustar, by a multi-step analysis. For this task, i) a structural analysis; ii) an estimation of the rock mass and discontinuity mechanical properties, iii) a rating of the rock mass quality, iv) and a numerical simulation of the stability are procedurally used. The results matched well with the field observations. They proved the poor stability of the career, showing a typical example of a bad slope-design. The application of such approaches can help stabilizing the mine and ensure the safety and a sustainable production.