Which one formula of talc

$\mathrm{Mg}_{2} \mathrm{SiO}_{4}(\mathrm{OH})_{2}$

$3 \mathrm{MgO} .4 \mathrm{SiO}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$

$3 \mathrm{MgO} \cdot 4 \mathrm{SiO}_{2} \cdot \mathrm{H}_{2} \mathrm{O}$

$\mathrm{Mg}_{3} \mathrm{Si}_{4} \mathrm{O}_{8}(\mathrm{OH})_{2}$