A downhole separator for separating solids from downhole well fluids comprises a cyclonic separation assembly. The assembly comprises a housing with at least one inlet port and an intake member disposed within the housing. The intake member includes a feed tube, a guide member disposed about the feed tube, and a vortex tube coaxially disposed within the feed tube. The assembly also comprises a cyclone body coaxially disposed within the housing and extending axially from the feed tube. In addition, the separator comprises an upper solids collection assembly coupled to the housing and configured to receive the separated solids from the cyclone body. Further, the separator comprises a lower solids collection assembly coupled to the housing and configured to receive the separated solids from the first solids collection assembly.