...Fig. 4 Difference in molar volume between spinelloids III and V in the Fe 2 SiO 4 -Fe 3 O 4 system (Fe-end-member) and Mg-bearing samples plotted as a function of Mg content. See text for details. Note the greater degree of scatter for the spinelloid V samples. ...

...C. R. Ross; Thomas Armbruster; D. Canil Abstract A spinelloid phase has been synthesized at 1200 °C, 7 GPa from the approximate composition Fe 5.2 Si 0.8 O 8 (Fa 40 -Mt 60 ). X-ray precession photographs indicated that it is probably isostructural with nickel aluminosilicate V. The photographs...

... = 8.3630(7) Å, V = 556.52(7) Å 3 ; space group Imma ], spinelloid-structured Fe 2 SiO 4 , a missing phase among the predicted high-pressure polymorphs of ferroan olivine, with the composition ( Fe 1.10 2 + Mg 0.80 Cr 0.04 3 + Mn 0.02 2 + Ca 0.02 Al 0.02 Na 0.01 ) Σ2.01 (Si 0.97 Al 0.03 ) Σ1.00 O 4...

... increases the likelihood that there is compositional continuity between wadsleyite and the spinelloid III phase field observed in the Mg-free system fayalite-magnetite. * E-mail: joseph.smyth@colorado.edu Manuscript handled by Jennifer Kung 25 02 2013 02 10 2013 © 2014...

.... The meteorite fragments contain the high-pressure phases ahrensite, coesite, stishovite, and an unnamed spinelloid with composition Fe 3– x Si x O 4 ( x ≈ 0.4). Other minerals include trevorite, Ni-Al-Mg-Fe spinels, magnetite, diopside, forsterite, clinoenstatite, nepheline, pentlandite, Cu-bearing troilite...

... that the incorporation of Fe occurs at two of four octahedral and at two of three tetrahedral sites. Apparently, Ca 4 Fe 1.5 Al 17.67 O 32 represents a new structure type exhibiting more pronounced structural modifications relative to the spinel aristotype compared with the so-called spinelloid structures. Furthermore...

... and 1000 K, new peaks are observed at about 670 and 1020 cm -1 . Above 1000 K,a direct transformation to forsterite occurs. The peaks that appear between 800 and 1000 K are attributed to a defective spinelloid that forms as an intermediate phase during the back-transformation of β-Mg 2 SiO 4 to forsterite...

... of the metastable olivine structure converting to more stable spinel or spinelloid structures or undergoing pressure-induced amorphization below 50 GPa. Rather, two new Raman bands appear above 30 GPa. On decompression the new bands are retained to 8 GPa. The spectral changes are interpreted as indicating...

...M. Fleischer; L. J. Cabri; A. Pabst Abstract Satoshi Matsubara, Akira Kato and Kozo Nagashima (1979) Iwakiite, Mn +2 (Fe +3 ,Mn +3 ) 2 O 4 , a new tetragonal spinelloid mineral from the Gozaisho mine, Fukushima Prefecture, Japan. Mineral. J. (Tokyo), 9 , 383-391. Copyright © 1980...

... spinelloid struc- materials from terrestrial impact craters and stony meteorites, because tures (Fig. 1). Rapid cooling and decompression during retrograde shock high-velocity collisions effectively simulate the high-pressure and high- metamorphism would have hindered the direct back-transformations...

..., zircon and a few minor mineral groups such as humites and datolites ( Deer et al. 1997 ). In addition, the silicate spinelloids are typically included here, but are not strictly orthosilicates as they contain Si 2 O 7 dimers. Titanite (CaTiSiO 5 ), though technically an orthosilicate, has a framework...