ABSTRACT: The study area is Alipaşa open pit albite mine which takes place in Aydın, Çine-Karpuzlu. Onlyleucocratic orthogneiss rock unit outcrops out in the mine. The albite mineralisation located in the N25Edirection with 900 m length and in the N65W direction with 120 m width. 45 m thickness below the presentmine base (395 m) of the open pit has been planned to be mined. The scope of this study is to determinethe optimum overall slope angle of the eastern slopes of the mine at the time which the mining operationsare terminated. In this context, based on the detailed field investigation and laboratory tests performed onthe rock material, numerical analyses for the deep slopes (H>100 m) were conducted. In the numericalmodelling, applicability of the finite element method (FEM) considering the Generalized Hoek-BrownCriterion and Equivalent Mohr-Coulomb parameters to the jointed rock slopes in the study area wasinvestigated. In this process, firstly five geotechnical cross-sections passing through the area affected fromlocal rock block slides were taken; secondly stability analyses of the overall slopes along these crosssections considering the variations of Geological Strength Index (GSI), seismic acceleration coefficient,slope angle and water table location (WTL) were conducted by using a two-dimensional FEM softwarePhase2 V.7.013. The causes and mechanisms of the slope instabilities, the factor of safety values (stressreduction factors: SRF) for each cross-section were determined. The results obtained from each criterionwere compared by statistical software SPSS V.15.0.1 to determine the optimum overall slope angle interms of the best fitting criterion for the orthogneisses.