What is Brittleness and Ductility?
All solids can be categorized as either ductile or brittle, as associated to the material’s plastic deformation when it undergoes loading. Ductility is the ability of the solid material to deform plastically under loading while Brittleness is when the material has the tendency to not deform plastically under tensile loading, but instead to fracture / break.
Brittle solids can present ductile behaviours, and ductile solids can present ductile behaviours… dependent on temperature and pressure.
- Calcite rocks such as limestone and dolostone – At shallow depths and lower temperatures may exhibit more brittle behaviours, but under higher temperatures and high confining pressures can exhibit more ductile behaviours
- Steel – while cold it is brittle, while warm it is more ductile
As modified from https://www.tulane.edu/~sanelson/eens1110/deform.htm
- Rocks with high quartz / silica content
- Cast iron, glass, concrete
- Rocks with high clay content
- Mild steel, tin, aluminum
One should also consider the difference between plastic deformation and elastic deformation of ductile materials. Plastic deformation will not remain in the deformed state (there may be some elastic rebound), while elastic deformation will go back to / close to the original state. Rocks such as marble and salt formations will behave elastically.
Also, in the case of fracturing of formations for oil and gas production, the ability of the formation to compress over and close in spite of the presence of proppant (proppant imbedment) should be considered.