In chemistry, a silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate ("fluorosilicate"), [SiF6]2-, but the silicate species that are encountered most often consist of silicon with oxygen as the ligand. Silicate anions, with a negative net electrical charge, must have that charge balanced by other cations to make an electrically neutral compound.
Silica, or silicon dioxide, SiO2, is sometimes considered a silicate, although it is the special case with no negative charge and no need for counter-ions. Silica is found in nature as the mineral quartz, and its polymorphs.
