Which type of crystal property involves the ability to generate an electric charge?

The correct choice pertains to piezoelectricity, which is a property of certain crystals that allows them to generate an electric charge when they are mechanically stressed. This phenomenon occurs due to the arrangement of atoms within the crystal structure, which causes an imbalance in electrical charge when pressure is applied.

In materials that exhibit piezoelectricity, such as quartz and tourmaline, the application of mechanical stress leads to a displacement of charges, resulting in an electrical potential. This property is significant in various applications, including sensors, actuators, and energy harvesting devices. Understanding piezoelectricity is essential for exploring how certain colored stones can be utilized in technologies that harness their unique electrical properties.

The other options, while relevant to the study of crystals and materials, do not directly relate to the generation of electric charge in the same manner as piezoelectricity.