This document discusses fractures and joints in rocks. It defines fractures, faults, and joints, and describes how they form from brittle deformation in response to stress. Joints form in sets with similar orientations and make up joint systems. The document discusses causes of fractures from tension and compression, and the different modes of cracking. It also describes the geometry of joints, including their orientation, scale, shapes, trajectories, spacing, intersections and terminations. Joint spacing depends on factors like bed thickness, lithology, structural position and strain.