Trimary use for Gilsonite is in restoring lost circulation. Due to bridging action of angular gilsonite solids at point of lost returns. Its effectiveness is due to particle-size distribution. Large and medium-size particles bridge forming a network which retains finer particles. Thus, a dense deposit is formed which is sealed by the cement. Decreasing the slurry weight by using an extender helps in controlling lost circulation by reducing the hydrostatic pressure.