Properties describe some quality of deformed and undeformed rocks such as mineralogical composition, texture, grain size, porosity, and strength. Similarly, fractures also have properties, which may be classified under geometric and physical properties. The geometric properties include fracture dimensions. For multiple structures, density and/or spacing are important geometric properties. Physical properties include elastic compliance or stiffness, surface roughness, resistivity, porosity and permeability among others. Some examples of factors are temperature, total stress, differential stress, fluid pressure, confining pressure, strain rate, grain size, porosity, solubility, and resistivity. Some of the properties are also factors such as grain size, texture, strength, solubility, and strain rate. Clearly, properties and factors overlap to a certain degree. Many of the properties can be found in handbooks and research papers. In this Knowledgebase we will focus on the properties that influence the failure of rocks and fluid flow through fractured rocks.