Tenacity

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. 

This article uses material from the Wikipedia article  Metasyntactic variable, which is released under the  Creative Commons Attribution-ShareAlike 3.0 Unported License.