olivine

Olivine, a captivating gemstone known for its vibrant green hues, derives its name from its olive-green to yellowish-green coloration. This mineral, composed of iron, magnesium, and silicate, belongs to the nesosilicate group.

Olivine's geological origins are primarily associated with igneous rocks, especially those in the mantle of the Earth. It forms as a result of high-temperature processes and is often found in volcanic basalt rocks and meteorites. Notable sources include regions with volcanic activity, such as Hawaii and the Canary Islands.

Peridot, a gem-quality olivine, has a distinctive green colour and is highly regarded for its use in jewellery. It is one of the few gemstones that come in only one colour—varying shades of green, from yellowish-green to deep, rich green.

Olivine has a unique history, being found in meteorites and some lunar samples, emphasizing its extra-terrestrial presence. Additionally, olivine's connection to volcanic activity and its place in the Earth's mantle make it a fascinating gemstone in the world of geology and mineralogy.

Click on the terms in the table below to discover their meaning

Click on the terms in the table below to discover their meaning

Name Olivine
Category Nesosilicate (Olivine group)
Chemical Formula (Mg, Fe2+)2SiO4
IMA Symbol Ol
Crystal System Orthorhombic
Crystal Habit Tabular or prismatic, typically with wedge-shaped terminations; commonly granular, compact, or massive.
Twinning Uncommon as simple twinning or cyclic twinning
Cleavage Good / Distinct
Fracture Conchoidal
Tenacity Brittle
Hardness
(Moh's Scale)		 6.5 - 7
Specific Gravity 3.275 - 4.392
Diaphaneity Transparent to translucent
Colour Green, yellow, brown, white, grey, blue-grey
Streak White
Lustre Vitreous to resinous
Optical Class Biaxial (+)
Refractive index n = 1.650 - 1.703
Birefringence δ = 0.032 - 0.038
Dispersion Rd = 0.020
Pleochroism X = Z = pale yellow; Y = yellow-orange, reddish brown
Clarity Type II
Notable Varieties Peridot, Ludwigite Peridot, Manchurian (Changbai) Peridot

References

Mineralogical Society of America. (2001). Fayalite. In J. W. Anthony, R. A. Bideaux, K. W. Bladh, & M. C. Nichols (Eds.), Handbook of Mineralogy. Chantilly, VA 20151-1110, USA: Mineralogical Society of America. Retrieved from https://www.handbookofmineralogy.org/pdfs/fayalite.pdf

Mineralogical Society of America. (2001). Forsterite. In J. W. Anthony, R. A. Bideaux, K. W. Bladh, & M. C. Nichols (Eds.), Handbook of Mineralogy. Chantilly, VA 20151-1110, USA: Mineralogical Society of America. Retrieved from https://www.handbookofmineralogy.org/pdfs/forsterite.pdf

Schumann, W. (2013). Gemstones of the World (17th ed.). (D. Shea, & N. Shea, Trans.) New York: Stirling Publishing Company.

About the Author

Daniel Gillespie is student of Web Development and the developer of Gemology 101. With a straightforward and informative approach, Daniel invites readers to explore the world of gemology, offering a valuable resource for both enthusiasts and those seeking knowledge about precious stones.