Abstract: An additive that increases the density of fluids containing a sized barite weighting agent. The wellbore fluid has rheological properties comparable to a conventional wellbore fluids but does not exhibit problems with sag and resulting variations in density. An illustrative embodiment is directed to a method for making the sized barite weighting agent and a method for using such sized barite weighting agent in a wellbore fluid. In one preferred embodiment the sized barite weighting agent has a particle diameter between 4 ?m to 15 ?m In another preferred embodiment, the additive has a D50 (by weight) of approximately 1 ?m to 6 ?m. In another preferred embodiment the additive has a D90 (by weight) of approximately 4 ?m to 8 ?m. The additive may be used in any wellbore fluid such as drilling, cementing, completion, packing, work-over (repairing), stimulation, well killing, and spacer fluid.