An introduction to the rock-forming minerals / Знакомство с породообразующими минералами

The members of the olivine group crystallize with orthorhombic symmetry, the structures consisting of independent SiO4 tetrahedra linked by divalent cations in six-fold coordination. In the (Mg,Fe)-olivines there is complete solid solution between Mg2SiO4 (forsterite) and Fe2SiO4 (fayalite); similarly the (Fe,Mn)-olivines form a continuous series. Olivine is a major constituent of ultrabasic plutonic rocks and olivines of metamorphic origin occur principally in rocks of ultramafic composition, in impure carbonates and in iron-rich sediments.