Stishovite (4.287 g/cc) is 47.3% denser than coesite and is structurally unlike the other silica minerals. The rutile-like stishovite structure consists of silicon atoms in sixfold coordination with oxygen; each oxygen atom is shared by three silicon atoms. Stishovite has refractive indices of 1.799 and 1.826. Stishovite is quite resistant to attack by cold …
The much larger volumes of stishovite synthesized under hydrous conditions relative to volumes of anhydrous stishovite calculated from its equation of state at the same pressures ( 29, 31, 32) provide primary evidence for considerable hydration.
An asteroid smashing into the earth and a laser pulsing through optical glass are very different phenomena, but both produce the extreme heat and pressures that …
An asteroid smashing into the earth and a laser pulsing through optical glass are very different phenomena, but both produce the extreme heat and pressures that instantaneously fuse silicon dioxide – the compound found in sand and glass – into the hard, dense and rare crystal known as stishovite.
Moreover, we construct a quantitative model of nucleation and grain growth, and compare its predictions with stishovite grain sizes observed in laser-induced damage and meteoroid impact events.
The ferroelastic post-stishovite transition in subducted mid-ocean ridge basalt (MORB) has been linked to these seismic features, but compressional and shear wave velocities ( VP and VS) and full elastic …
These findings attest to a novel mechanism of the formation of stishovite in the solid state and provide an explanation for similar microstructural occurrences of stishovite in impact-metamorphic rocks and shocked meteorites.
The solubility and incorporation mechanisms of hydrogen in synthetic stishovite as a function of Al2O3 content have been investigated. Mechanisms for H incorporation in stishovite are more complex than previously thought. Most H in stishovite is incorporated via the Smyth et al. (Am Mineral 80:454–456, 1995) model, where H …
Nanocrystalline bulk stishovite, with pure SiO 2 composition, was synthesized under high pressure and temperature. We found that this material has an extremely high fracture toughness (∼13 MPa m 1/2 ), nearly eight times higher than that of stishovite single crystal. The measured Vickers hardness of this material was ∼29 GPa …
These findings attest to a novel mechanism of the formation of stishovite in the solid state and provide an explanation for similar microstructural occurrences of …
Microcrystals of coesite and stishovite were discovered as inclusions in amorphous silica grains in shocked melt pockets of a lunar meteorite Asuka-881757 by micro-Raman spectrometry, scanning electron microscopy, electron back-scatter diffraction, and transmission electron microscopy.
Quartz and/or cristobalite in eucrite were transformed into denser minerals, coesite and stishovite, under transient high-pressure and high-temperature conditions. Coesite and stishovite probably formed simultaneously under pressures of similar magnitudes but under different temperature conditions.
The high-pressure silica polymorphs coesite and stishovite were synthesized under water-saturated conditions from a natural granitic composition doped with Li and B. Experiments were performed in a Multi-Anvil apparatus between 4 and 9.1 GPa and 900 and 950 °C, based on the conditions of a subducting continental crust as realistic for the …
Stishovite, which is one of the dominant minerals in mid-ocean ridge basalt, continental crust and sediment layers, possesses significant anisotropic elasticity and has high potential to contribute to the observed seismic anisotropy.
[1] In situ P - V - T measurements of stishovite have been performed throughout its stability field from 17 to 54 GPa and from 300 to 1700 K, by using a sintered-diamond multianvil apparatus and synchrotron radiations. The P - V - T equation of state of stishovite was precisely determined on the basis of the Mie-Grüneisen-Debye model …
In the present study, we show evidences of a new pathway, a fracture-induced solid-state amorphization of polycrystalline stishovite, by careful observations of fracture surfaces of samples with ...
Stishovite (rutile-type SiO 2) is the archetype of dense silicates and may occur in postgarnet eclogitic rocks at lower-mantle conditions. Sound velocities in stishovite are fundamental to …
The rapid liquidus crystallization of stishovite only in hot spots generated in porous material is an alternative formation mechanism to the widely accepted theory of …
Unit cell parameters acquired at 300 K and high pressure are summarized in Fig. 2 and Table 1. The much larger volumes of stishovite synthesized under hydrous conditions relative to volumes of anhydrous stishovite calculated from its equation of state at the same pressures ( 29, 31, 32) provide primary evidence for considerable hydration.
It is extremely difficult to realize two conflicting properties—high hardness and toughness—in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular …
Transmission electron microscopy and electron diffraction show that the martian meteorite Shergotty, a shocked achondrite, contains a dense orthorhombic SiO 2 phase similar to post-stishovite SiO 2 with …
Stishovite is one of the major mineral components in subducting oceanic crust, yet the capacity of stishovite to incorporate water beyond at lower mantle conditions remains speculative.
These reactions in diamond-forming carbonate–silicate–carbon melts provided the formation of stishovite, which was captured as a paragenetic inclusion by diamonds and transported to the Earth's surface by magmas. The genesis of stishovite under the terrestrial conditions is controlled by global mantle convection as well.
The coesite-stishovite phase transition is considered the most plausible candidate to explain the X-discontinuity observed at around 300 km depth in a variety of tectonic settings. Here, we investigate the …
The post-stishovite phase transition occurs at 24.3 (5) GPa (at 298 K), far lower than for pure silica at 50–60 GPa. Our results suggest that the rutile–CaCl 2 transition in natural stishovite (with 5 wt % Al 2 O 3) should occur at ≈30 GPa or ≈1,000-km depth at mantle temperatures.
The angle-dispersive powder X-ray diffraction analysis confirmed single phase stishovite. In order to release the non-hydrostatic stress in stishovite, we intermixed the stishovite with NaCl in the proportion of 2:1 by weight and this was used for the P-V-T experiment.
The thickness of the stishovite layer in the sample is estimated from the stishovite volume fraction times the crystalline thickness of the sample. Because the samples were initially glass and loaded into the diamond cell without a pressure medium, only the hottest portion of the sample was converted to the stable, high-pressure phases.
Transmission electron microscopy and electron diffraction show that the martian meteorite Shergotty, a shocked achondrite, contains a dense orthorhombic SiO 2 phase similar to post-stishovite SiO 2 with the α-PbO 2 structure. If an SiO 2 mineral exists in Earth's lower mantle, it would probably occur in a post-stishovite SiO 2 structure. The …
Although they investigated the pure silica phases, the water solubility of stishovite dramatically increases with increasing alumina content, which is the second major component in stishovite and poststishovite ( 14 – 16, 19, 20 ), via the Si 4+ = Al 3+ + H + charge-coupled substitution ( 21 – 24 ).
Moreover, we construct a quantitative model of nucleation and grain growth, and compare its predictions with stishovite grain sizes observed in laser-induced damage and meteoroid impact events.
The Mineral stishovite. Stishovite is an extremely rare mineral forming only from the impact of a meteorite through the metamorphism of Quartz at extremely high temperatures. It is interesting to note that Stishovite is scientifically classified as an oxide and not as a silicate, even though it is polymorph ous with Quartz.
While stishovite and coesite are thermally metastable up to 500 and >1000 °C, respectively, their hydrothermal metastability is below 150 and 200 °C, respectively. The thermally induced conversion of stishovite and coesite leads to amorphous products, whereas the hydrothermally induced conversion leads to crystalline quartz.
Here we present in situ pump–probe XRD measurements on shock-compressed fused silica, revealing an amorphous to crystalline high-pressure stishovite …
The coexistence of coesite and stishovite would be due to the significant temperature gradient in the silica grain. The dynamic event that formed both coesite and stishovite is the most intense impact incident recorded in Béréba. We could constrain a pressure condition recorded in Béréba using high-pressure polymorphs.
Stishovite was formed by heating α-quartz or amorphous silica at pressures of up to 92 GPa; on heating at 108 and 124 GPa, however, the materials crystallized into a CaCl2-type structure, which ...
The kyanite/stishovite fit is well within the range of misfits exhibited by known exsolution relationships and the spinel/stishovite fit improves to better than 2% for comparison of 9 unit cells of stishovite with 2 unit cells of spinel.
The role of stishovite in transporting water in subducting slabs has been a subject of debate for several decades. Here we investigated stishovite's water solubility and its potential role in water transportation as a function of temperature from 1300 to 2100°C at 22 GPa. Under water-saturated conditions, high-quality, Al-free stishovite …
For the first time in the sixty years since the synthesis of stishovite, we report unambiguous evidence of stishovite formed in the deep Earth. A minimum pressure of about 7.5 GPa at 1000 °C is …
Single-crystal elasticity of stishovite was examined using a new experimental technique and an empirical macroscopic model. Employing high-frequency r…
