In ionic bonding the ions are joined together in the cyrstal structure by the attraction of their unlike electrostatic charges. One ion has a negative charge, the other a positive charge. Ionic-bonded minerals are characterized by: moderate hardness and specific gravity fairly high melting and boiling points very poor conductors of electricity and heat Because the electrostatic charge is spread over the whole surface of the atom, this bond type is not highly directional and the symmetry of the resulting crystal is generally high.

Bonding / Crystal Chemistry