Forsterite (olivine) Mg₂SiO₄

Unit cell

Lattice constants

a = 4.754 Å, b = 10.205 Å, c = 5.984 Å; α = 90°, β = 90°, γ = 90°

Cell volume

290.3 ų

Atoms in the cell

28 (Mg 8, Si 4, O 16)

Formula units Z

4

Calculated density

2.58 g cm⁻³

Shortest contact

1.479 Å

Coordination

Mg

CN 6 at 2.07 Å (6 O)

Si

CN 4 at 1.48 Å (4 O)

O

CN 1 at 1.55 Å (1 Si)

About the structure

• Isolated SiO₄ tetrahedra in an approximately hexagonal close-packed oxygen array, with Mg²⁺ in half of the octahedral holes (two distinct sites, M1 and M2).
• The magnesium end-member of olivine, the main mineral of the upper mantle; LiFePO₄ (also in this lab) is the same framework with Li and Fe on the M sites.
• Coordinates from the Crystallography Open Database, entry 1572966 (open data); hydrogen and water sites with partial occupancy below 0.5 are left out.

Atom positions (fractional, one cell)

Z, coordination numbers, distances, density and packing on this page are computed from these coordinates.