 When covalent bonds link long chains of atoms in large molecules, however (as in polymers such as nylon), or when covalent bonds extend in networks through solids that are not composed of discrete molecules (such as diamond or quartz or the silicate minerals in many types of rock) then the structures that result may be both strong and tough, at least in the direction oriented correctly with networks of covalent bonds.Also, the melting points of such covalent polymers and networks increase greatly.In a simplified view of an "ionic" bond, the bonding electron is not shared at all, but transferred.