Silicon dioxide (SiO2) and diamonds are best described as

Silicon dioxide (SiO₂) and diamonds are best described as network solids with covalent bonding.

Covalent-network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material. Silicon (IV) oxide has continuous three-dimensional network of SiO ₂ units and diamond has sp3 hybridization.