Editing Peridot (section)

=== Crystal structure ===
[[File:Atomic_structure_of_olivine_1.png|thumb|The atomic scale structure of olivine looking along the ''a'' axis. Oxygen is shown in red, silicon in pink, and magnesium/iron in blue. A projection of the unit cell is shown by the black rectangle.]]
The molecular structure of peridot consists of isomorphic olivine, silicate, magnesium and iron in an [[orthorhombic crystal system]]. In an alternative view, the atomic structure can be described as a hexagonal, close-packed array of oxygen [[ion]]s with half of the octahedral sites occupied by magnesium or iron ions and one-eighth of the tetrahedral sites occupied by silicon ions.