Abstract: Compositions of lost circulation materials are provided that are useful for identifying the location of fluid loss in a wellbore. The compositions include additives which enhance a property of the composition such that they can be detected by an LWD or MWD tool capable of measuring the property when the composition is deployed in a region of loss, and can be distinguished by the LWD or MWD tool from the formation and mud fluid. Methods are also provided for using the composition to detect the location of fluid loss and for controlling the loss of fluid from the wellbore. The methods involve deploying the compositions in loss regions by adding the compositions to drilling mud, and measuring a property of the compositions using an LWD or MWD tool.