Calculation of the properties of dislocations by computer simulations requires, among other things, the availability of accurate interatomic potentials, ideally with ab-initio quality. For crystals with large unit cells and complex crystal structures, such as most minerals, the number and size of the calculations may severely limit the applicability of a full ab-initio approach. In this paper we present an investigation of the dislocation properties of coesite, a mineral with a relatively large unit cell, carried out with a force field developed for silica based on a parametrization to ab-initio data. Two-dimensional generalized stacking fault energy surfaces for basal and prismatic planes are considered for a global search of the possible dissociation paths in partial dislocations. Test calculations show negligible differences between the energy surfaces calculated with the force field and with ab-initio methods. Five different coesite slip systems are investigated: (010), (010),(010), (001), and ( ̄101). Dislocation core structures and critical stresses are determined byusing the Peierls-Nabarro-Galerkin approach. While  and  (screw) dislocations share a similar core structure,  differs substantially by showing a much larger split between partial dislocations. The lattice friction experienced by (010) is found to be close to those of (010) and (010), confirming the pseudohexagonal symmetry suggested by experiments.