Oxides and sulfides (such as ZnO, ZnS, and BeO) containing smaller cations tend to have tetrahedral coordination (i. e., the coordination number of both the cation and the anion is 4). The same structure is also shown by the covalent compounds, such as SiC, BN, and GaAs. This structure class is named after the mineral zinc — blende in which the anions (S2~) form the FCC sublattice, and only half of the available tetrahedral sites are filled with the cations (Zn2+), as depicted in Figure 2.23. Note the similarity between the zincblende and diamond structures (refer back to Figure 2.19).