olivine

olivine
Name	Olivine
Category	Nesosilicate
Formula	(Mg,Fe)2SiO4
System	Orthorhombic
Color	Green to yellow-green
Habit	Granular, idiomorphic to anhedral grains
Cleavage	Poor
Hardness	6.5–7
Luster	Vitreous to greasy
Gravity	3.2–4.4

olivine is a magnesium-iron nesosilicate mineral that commonly forms in mafic and ultramafic igneous rocks and in some metamorphic contexts. It is represented by a solid-solution series between forsterite and fayalite and is a primary phase in the Earth's upper mantle, basaltic lavas, and meteorites. Olivine's composition, crystal structure, and alteration behavior make it central to studies in petrology, geochemistry, planetary science, and economic geology.

Mineralogy and Composition

Olivine is a solid solution series between the magnesium endmember forsterite and the iron endmember fayalite; historical and modern work by figures such as Gustav Rose, Friedrich Mohs, Jöns Jakob Berzelius, James Dwight Dana, and institutions like the Smithsonian Institution and the Natural History Museum, London contributed to its classification. Compositional variations are characterized by magnesium number (Mg#) and iron content, with trace elements including nickel, manganese, and chromium, analyzed in laboratories at facilities such as Lawrence Berkeley National Laboratory and the Max Planck Institute for Chemistry. Major-field surveys by teams from the United States Geological Survey, British Geological Survey, Geological Survey of Japan, and university departments at University of Oxford, Harvard University, Massachusetts Institute of Technology, and California Institute of Technology document olivine in diverse tectonic settings from the Mid-Atlantic Ridge to the Kola Peninsula. Petrologists referencing classic works by N.L. Bowen, Yuri A. Babaev, George W. Morey, and Hatten S. Yoder examine phase relations in the system forsterite–fayalite–silica under variable pressure and temperature.

Crystal Structure and Properties

Olivine crystallizes in the orthorhombic system with isolated SiO4 tetrahedra coordinated to divalent cations in M1 and M2 sites; structural studies by researchers at Birkbeck, University of London, ETH Zurich, Carnegie Institution for Science, and Argonne National Laboratory elucidate cation ordering and defect structures. Physical properties such as refractive indices, birefringence, and absorption spectra have been cataloged by scientists at the Royal Society, American Geophysical Union, and museums including the Natural History Museum, Vienna and the Field Museum. High-pressure experiments performed at facilities like CERN, Oak Ridge National Laboratory, Institut Laue–Langevin, and Tokyo Institute of Technology constrain phase transformations to spinel and perovskite structures, linking olivine behavior to deep mantle mineralogy explored by groups at Scripps Institution of Oceanography and the GEOMAR Helmholtz Centre for Ocean Research Kiel.

Formation and Occurrence

Olivine is a primary mineral in peridotite, dunite, harzburgite, and basaltic magmas erupted at locales such as Hawaii, Iceland, Sicily, Mount Etna, Mount Kilimanjaro, and the Deccan Traps; field studies by teams from University of Hawaii at Manoa, University of Iceland, Università degli Studi di Palermo, and Indian Institute of Science document outcrops and lava flows. Mantle xenoliths delivered by kimberlites from Kimberley, South Africa, Yakutia, and Siberia provide olivine-rich samples studied by researchers at University of Cape Town, Moscow State University, and Utrecht University. Extraterrestrial olivine occurs in meteorites examined at the Lunar and Planetary Institute, in martian meteorites curated at NASA Johnson Space Center, and on planetary surfaces mapped by missions such as Voyager, Galileo, Cassini–Huygens, Mars Reconnaissance Orbiter, and Hayabusa.

Economic and Industrial Uses

Olivine-bearing rock is exploited for foundry sand, refractory materials, and slag conditioning in steelmaking by industrial firms like Midrex Technologies, Outokumpu, and operations cataloged by national agencies including the Australian Bureau of Statistics and the United States Department of the Interior. Industrial mineral companies such as Imerys, Sibelco, and Mineral Commodities Limited process olivine for applications in abrasives and filtration media. Research on carbon sequestration via olivine carbonation has been advanced by teams at Carnegie Mellon University, Stanford University, ETH Zurich, and policy assessments by the Intergovernmental Panel on Climate Change and the European Commission.

Role in Planetary Science and Geochemistry

Olivine's presence in lunar samples returned by Apollo 11, Apollo 15, and Apollo 17 missions and in chondritic and achondritic meteorites studied at Johnson Space Center underpins models of planetary differentiation developed by scientists such as Harold Urey, Victor Goldschmidt, Hermann von Helmholtz, and modern investigators at Caltech and MIT. Spectroscopic detections of olivine on Mars by instruments on Mars Reconnaissance Orbiter and on asteroids Eros and Itokawa by NEAR Shoemaker and Hayabusa informed mission planning at agencies including NASA, ESA, JAXA, and Roscosmos. Geochemical partitioning of nickel, cobalt, and platinum-group elements between olivine and sulfide phases is critical to exploration programs run by companies like Barrick Gold, Rio Tinto, and BHP and to global surveys by organizations such as the World Bank and United Nations geological initiatives.

Alteration, Weathering, and Metamorphism

Olivine weathers rapidly to iddingsite, serpentine-group minerals, chlorite, and magnetite in oxidative, hydrous environments; seminal petrographic descriptions originate from scholars at University of Cambridge, University of Edinburgh, and the Geological Society of London. Serpentinization experiments by groups at Woods Hole Oceanographic Institution, Lamont–Doherty Earth Observatory, Monash University, and University of Toronto probe hydrogen generation, abiotic organic synthesis, and implications for chemosynthetic ecosystems near Mid-Ocean Ridge hydrothermal vents investigated during expeditions led by vessels such as RV Atlantis and RV Knorr. Industrial remediation concepts leveraging olivine alteration are discussed in reports from the Environmental Protection Agency and the European Environment Agency.

Identification and Analytical Techniques

Identification of olivine in hand sample, thin section, and powder relies on optical microscopy, X-ray diffraction, electron microprobe analysis, and Raman spectroscopy practiced in labs at University of California, Berkeley, Imperial College London, Peking University, and Universidad Nacional Autónoma de México. Advanced techniques including secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and synchrotron-based X-ray absorption spectroscopy at facilities such as Diamond Light Source, Advanced Photon Source, European Synchrotron Radiation Facility, and SLAC National Accelerator Laboratory provide trace-element and isotopic resolution used by teams from AGU, GSA, and the Mineralogical Society of America. Geochemical databases maintained by the Geological Survey of Canada, USGS National Geochemical Database, and university consortia support comparative studies and resource assessments.

Category:Silicate minerals