Sio4 4– tetrahedra join with ions to produce the mineral olivine in the rock peridotite.

The independent SiO4 4- tetrahedra join with the Mg2+ and Fe2+ ions to generate the mineral olivine in the rock peridotite.  

Olivine is the naming of group-producing minerals, which are usually found in ultramafic and mafic rocks, like gabbro, basalt, diabase, dunite, and peridotite. They are generally green in appearance and exhibit constituents, which generally range between Fe2SiO4 and Mg2SiO4.