Structure of $\left.{\mathrm{Na}}_2{\left[{\mathrm{B}}_4{\mathrm{O}}_5\mathrm{OH}\right)}_4\right]\cdot 8{\mathrm{H}}_2\mathrm{O}$ contains:

 $\left.{\mathrm{Na}}_2{\left[{\mathrm{B}}_4{\mathrm{O}}_5\mathrm{OH}\right)}_4\right]\cdot 8{\mathrm{H}}_2\mathrm{O}$ is Borax

It has two tetrahedral units and two triangular units.
The additional water molecules are connected to the metal ions, and the ion is ${\mathrm{B}}_4{\mathrm{O}}_5(\mathrm{OH}{)}_4^{-}$