There is provided a method of fabricating a composite material, the method comprising providing borehole solids originating from a borehole in the earth and embedding the borehole solids in a base material thereby forming the composite material, wherein the base material comprises a polymer. According to an embodiment, the borehole solids contain oil, e.g. on a surface thereof. The oil containing borehole solids may be preprocessed before embedding or may be directly embedded in the base material without preprocessing. Such embodiments allow for a recycling of oil contaminated borehole solids while providing a resource for a filler for polymers.