Forsterite is a naturally occurring mineral that belongs to the olivine group.
It has the chemical formula \(\text{Mg}_2\text{SiO}_4\), which clearly indicates that it is a magnesium silicate.
It is often found in mafic and ultramafic igneous rocks and is a significant source of magnesium.
Hence, Forsterite is a mineral of magnesium (Mg).