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Silicate minerals
About: Silicate minerals is a research topic. Over the lifetime, 1794 publications have been published within this topic receiving 67064 citations.
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TL;DR: In this article, the occurrence and mineral chemistry of chromite and its high pressure phase xieite in the Suizhou meteorite were studied by different modern micromineralogical techniques.
Abstract: The occurrence and mineral chemistry of chromite and its high-pressure phase xieite in the Suizhou meteorite were studied by different modern micromineralogical techniques. Three types of occurrences for chromite were observed in the Suizhou L6 chondrite: coarse chromite grains, cluster of chromite fragments in molten plagioclase, and exsolution lamellar chromite in olivine. All the chromite grains of the first two types are remarkably similar in chemical compositions, but the composition of exsolution chromite is inhomogeneous and variable in Al2O3 content. Xieite is a post-spinel CT-phase of chromite firstly found in the Suizhou meteorite. Three types of occurrences of xieite have also been revealed in this meteorite: coarse xieite grains, complex three-zone-grains consisting of the inner xieite, the intermediate lamellae-like CF-phase and the outer chromite phase, and two-phase-grains consisting of xieite and one of the high-pressure silicate minerals lingunite, ringwoodite or majorite. The curved boundary between xieite and the silicate half in two-phase grains is indicative of some partial or even full melting of the silicate phase. EPMA and EDS results show that the compositions of xieite inside/contacting the shock veins are also identical to that of chromite outside the veins. However, some element diffusion appeared in between the xieite and the silicate half in the two-phase grains, namely, some of Al3+ from lingunite, or Fe2+ from ringwoodite migrated to xieite, and some of Cr3+ migrated from xieite to lingunite or ringwoodite. Majorite in two-phase grains shows remarkable decrease of SiO2 and MgO, and notable increase of Al2O3 and CaO, indicating that its host mineral pyroxene was fully molten and mixed with the surrounding silicate melt of the vein matrix. The complexity in mineral chemistry of these two-phase grains in shock veins can be explained by the much higher shock peak temperature in shock veins (1800–2000°C) than in unmelted main body (∼1000°C), and by the much lower density of the silicate minerals (2.6–3.3 g/cm3) than that of chromite (4.43 g/cm3). Being a refractory and a relatively high-impedance material, chromite is chemically more stable and easier to reflect shock wave into the silicate half causing the partial or even full melting of silicate phases, upon which some diffusion of elements between the two phases themselves, or even mixing of molten pyroxene and the surrounding silicate melt.
10 citations
01 Jan 2007
TL;DR: In this paper, the dispersion mechanisms of sodium hexametaphosphate on the four aluminum-silicate minerals were confirmed by measurements of zeta potentials and theoretical calculations of DLVO.
Abstract: Influences of phosphates on the dispersion of diaspore,kaolinite,illite and pyrophyllite were systematically investigated by sedimentation experiments.The dispersion mechanisms of sodium hexametaphosphate on the four aluminum-silicate minerals were confirmed by measurements of zeta potentials and theoretical calculations of DLVO.The results show that the dispersity order of phosphates from strong to weak is as follows: sodium hexametaphosphate,sodium pyrophosphate,trisodium phosphate.The absolute value of zeta potentials of aluminum-silicate minerals and the electrostatic repulsion among mineral particles increase with addition of sodium hexametaphosphate.The space steric effects among mineral particles are also intensified due to the adsorption of sodium hexametaphosphate on the surface of aluminum-silicate minerals,then the steric repulsion among particles is enhanced.
10 citations
TL;DR: The mineralogy of some soils developed on tills derived from basalt and andesite of Lower Old Red Sandstone age has been investigated by X-ray diffraction and optical and scanning electron microscopy as discussed by the authors.
10 citations
TL;DR: In this article, the 2.5-3.3 micron wavelength region of VI Cyg 12, AFGL 2205, and AFGL 2885 were obtained in a search for bound water, hydroxyl groups, and hydrated minerals in interstellar dust.
Abstract: Spectra in the 2.5-3.3 micron wavelength region of VI Cyg 12, AFGL 2205, and AFGL 2885 were obtained in a search for bound water, hydroxyl groups, and hydrated minerals in interstellar dust. No new absorption bands were found. Comparison of expected strengths of bands of serpentine and chlorite-like minerals with the data suggests that less than 25 percent and 50 percent, respectively, of the silicate in the grains is composed of these materials.
10 citations
TL;DR: In this paper, the authors assess the solubilization of silicates during the chemical and bacterial leaching of finely ground black schist in shake flasks and show that the dissolution of main constituent elements from silicate minerals was a function of the pH of the leach solution and no direct role of bacterial action on the solusability of the silicates was evident.
10 citations