Methods, systems, and computer-readable medium to perform operations for identifying fracture barriers in a well. The operations include converting rebound hardness values of a rock specimen from the well to unconfined compressive strength (UCS) values, where each of the rebound hardness values corresponds to a respective coordinate of a measurement grid imposed on the specimen. The operations further include, for each column of the grid, plotting the UCS values versus depth. Further, the operations include mapping, based on a maximum UCS value and a minimum UCS value, a relative strength contour plot for the specimen. Yet further, the operations include mapping, based on a fixed strength range, an absolute strength contour plot for the specimen. In addition, the operations include determining, based on the relative strength contour, the absolute strength contour, and mineralogy of the rock specimen, that the rock specimen is indicative of a fracture barrier in the well.