Olivine (Peridot)

Orthorhombic (Mg,Fe)₂SiO₄ series making up over 50% of Earth's upper mantle; its gem variety is peridot.

Specifications & Metrics

type

Nesosilicate Mineral

formula

(Mg,Fe)₂SiO₄ (forsterite–fayalite series)

crystal system

Orthorhombic

hardness

6.5–7.0 Mohs

refractive index

1.630–1.690

density

3.2–4.5 g/cm³

melting point

≈1,900 °C (forsterite); ≈1,200 °C (fayalite)

Core Principles & Analysis

• Olivine and its high-pressure structural variants constitute over 50% of Earth's upper mantle, with Mg-rich olivine stable to depths of about 410 km.
• Transparent olivine is the gemstone peridot, with the finest historical source on Zabargad Island in the Red Sea.
• Olivine grains eroded from lava color Papakōlea Beach, Hawaii green, and Norway supplies about 50% of the world's industrial olivine, a substitute for dolomite in steel works.

Sources

• Wikipedia: Olivine