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| Ringwoodite | |
|---|---|
| Name | Ringwoodite |
| Category | Inosilicate |
| Formula | (Mg,Fe)2SiO4 |
| Crystal system | Isometric |
| Symmetry | Fd-3m |
| Color | Blue to purple in natural inclusions; colorless to greenish in synthetic samples |
| Habit | Granular, inclusion |
| Cleavage | None |
| Fracture | Conchoidal |
| Mohs | 7.5–8 |
| Luster | Vitreous |
| Refractive index | n = 1.78–1.83 (approx.) |
| Density | 3.9–4.1 g/cm3 |
| Diaphaneity | Transparent to translucent |
Ringwoodite is a high‑pressure polymorph of olivine with the nominal composition (Mg,Fe)2SiO4. It is stable at pressures characteristic of the Earth's mantle transition zone and has been identified in natural inclusions and synthesized in laboratories, playing a central role in models of mantle mineralogy, water storage, and seismic discontinuities.
Ringwoodite is named for the Australian geochemist and mineralogist after whom it was titled, recognized for work linking mineral phase equilibria to planetary interiors. The phase is isostructural with the spinel group and occurs where pressure and temperature conditions drive olivine to transform into denser polymorphs. Its significance spans studies by institutions such as the Australian National University, Carnegie Institution for Science, and Massachusetts Institute of Technology, and figures including Ted Ringwood, Walter M. Brookes and teams that investigate deep Earth processes at facilities like the Geological Survey of Japan.
Ringwoodite has the spinel-type structure with Si in octahedral coordination and Mg/Fe distributed over multiple sites; this arrangement contrasts with the olivine lattice found in shallower lithologies. Its formula ranges from magnesium-rich to iron-bearing endmembers, defined and refined in works linked to researchers from Harvard University, University of Cambridge, and ETH Zurich. The cubic symmetry (Fd-3m) yields three-dimensional frameworks that influence elastic moduli measured at laboratories such as Lawrence Livermore National Laboratory and Vanderbilt University. Structural investigations employ methods developed at facilities like Oak Ridge National Laboratory and Argonne National Laboratory using spectroscopy and diffraction techniques pioneered at Brookhaven National Laboratory.
Ringwoodite forms by the pressure‑induced transformation of olivine at depths corresponding to the mantle transition zone (~410–660 km), linked to phase transitions documented during expeditions supported by the United States Geological Survey and field studies in regions including Hawaii and Gujarat. It can also form in shocked meteorites during impacts involving bodies such as Vesta and Hoba and has been recovered as inclusions in diamonds sourced from cratons like the Kaapvaal Craton and Slave Craton. Experimental petrology work at institutes such as California Institute of Technology and University of Tokyo reproduces these conditions using multi‑anvil presses and diamond anvil cells, techniques advanced at the Max Planck Institute for Chemistry and RIKEN.
Ringwoodite exhibits high density and incompressibility relative to olivine, with a Mohs hardness comparable to many mantle phases; these properties are characterized in studies affiliated with Smithsonian Institution mineral collections and analyzed by groups at Johns Hopkins University and University of Chicago. Optical behavior, including pleochroism and absorption features observed in natural blue inclusions, has been documented by mineralogists associated with Natural History Museum, London and American Museum of Natural History. Elastic, seismic, and rheological parameters have been measured under variable temperature by teams at Scripps Institution of Oceanography and Woods Hole Oceanographic Institution.
Ringwoodite's stability field helps define the seismic discontinuities at ~410 km and ~660 km, phenomena extensively studied in seismology by groups at Seismological Society of America, USArray, and the International Seismological Centre. Its capacity to host hydroxide (OH−) in interstitial sites suggests a significant role in deep water storage, a topic explored in collaborative projects involving NASA, European Space Agency, and observatories such as Lamont–Doherty Earth Observatory. Models incorporating ringwoodite influence geodynamic interpretations generated by researchers at Princeton University, Stanford University, and the Geological Survey of Canada, informing hypotheses about mantle convection, plume generation near Iceland, and subduction processes beneath regions like Japan and Alaska.
Natural ringwoodite has been identified as inclusions within superdeep diamonds recovered by mining companies and analyzed in laboratories at institutions including University of Alberta, Monash University, and University of Western Australia. The discovery of hydrous ringwoodite in a diamond inclusion prompted investigations by teams from University of Nevada, Reno and University of Queensland into the global deep water cycle. Synthetic ringwoodite is produced using high‑pressure apparatuses at centers such as Geological Survey of Japan, Carnegie Institution for Science, and GFZ German Research Centre for Geosciences, enabling experimental determination of phase relations, diffusion, and electrical conductivity measured at Los Alamos National Laboratory and Pacific Northwest National Laboratory.
Ringwoodite was first synthesized and characterized following high‑pressure mineral physics advances credited to researchers at Australian National University and later identified in nature within diamonds studied by teams from Smithsonian Institution and University of Toronto. The mineral was named to honor Ted Ringwood for contributions linking petrology to planetary differentiation, paralleling work on mantle phase transitions by scientists from University of California, Berkeley, Brown University, and Yale University. Ongoing research continues through collaborations involving National Science Foundation grants, international consortia such as the International Union of Geodesy and Geophysics, and specialized facilities including the High Pressure Collaborative Access Team.
Category:Minerals