In mineralogy, tenacity is a mineral's behavior when deformed or broken. Common terms Brittleness: The mineral breaks or powders easily. Most ionic-bonded minerals are brittle. Malleability: The mineral may be pounded out into thin sheets. Metallic-bonded minerals are usually malleable. Ductility: The mineral may be drawn into a wire. Ductile materials have to be malleable as well as tough. Sectility: May be cut smoothly with a knife. Relatively few minerals are sectile. Sectility is a form of tenacity and can be used to distinguish minerals of similar appearance. Gold, for example, is sectile but pyrite ("fool's gold") is not. Elasticity: If bent, will spring back to its original position when the stress is released. Plasticity: If bent, will not spring back to its original position when the stress is released. It stays bent. In contrast, flexibility is the ability of a material to deform elastically and return to its original shape when the applied stress is removed. References Mineralogy Deformation (mechanics) Materials science