Silicate having one monovalent corner oxygen atom in each tetrahedron unit is:

The general formula of sheet or phyrosilicate is ${\left({\mathrm{Si}}_2{\mathrm{O}}_5\right)}_{\mathrm{n}}^{2\mathrm{n}-}$. each SiO₄ tetrahedron shares three oxygen atoms with others and thus by
forming two dimensional sheets these silicate can be cleared easily just like graphite.