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hydrohematite

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Journal Article
Published: 01 February 2015
American Mineralogist (2015) 100 (2-3): 570–579.
... balance is achieved by iron vacancies. Prior researchers have suggested that the defective hematite structures form unique phases called “protohematite” and “hydrohematite.” Infrared and Raman spectroscopic studies have assigned a lower-symmetry space group to “hydrohematite” ( R 3 c ) relative...
FIGURES | View All (11)
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The compositional relationships among ferrihydrite, <span class="search-highlight">hydrohematite</span>, and stoi...
Published: 01 September 2023
Figure 1. The compositional relationships among ferrihydrite, hydrohematite, and stoichiometric hematite. Synthetic hydrohematite products in this study exhibited refined Fe occupancies in the range of 0.80 to 0.90. (Color online.)
Journal Article
Published: 01 September 2023
American Mineralogist (2023) 108 (9): 1720–1731.
...Figure 1. The compositional relationships among ferrihydrite, hydrohematite, and stoichiometric hematite. Synthetic hydrohematite products in this study exhibited refined Fe occupancies in the range of 0.80 to 0.90. (Color online.) ...
FIGURES | View All (13)
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Schematic diagram of chemical composition of natural <span class="search-highlight">hydrohematite</span> and hydr...
Published: 20 July 2021
Figure 2. Schematic diagram of chemical composition of natural hydrohematite and hydrogoethite. Fe occ refers to Fe occupancy. Ideal hydrohematite described by Breithaupt and Hermann in the 1840s ( Hermann, 1844 ; Breithaupt, 1847 ) locates midway between stoichiometric hematite (Hm
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Stacked TRXRD patterns showing the crystallization of <span class="search-highlight">hydrohematite</span> (Hyhm, ...
Published: 01 September 2023
Figure 2. Stacked TRXRD patterns showing the crystallization of hydrohematite (Hyhm, red peaks) and goethite (Gt, yellow peaks) from 2-line ferrihydrite (Fh) at 90 °C pH 11. Zoom-in plot showed that the ratio of starred peaks at (214) (left) and (300) (right) in hydrohematite is sensitive to time
Journal Article
Journal: Geology
Published: 20 July 2021
Geology (2021) 49 (11): 1343–1347.
...Figure 2. Schematic diagram of chemical composition of natural hydrohematite and hydrogoethite. Fe occ refers to Fe occupancy. Ideal hydrohematite described by Breithaupt and Hermann in the 1840s ( Hermann, 1844 ; Breithaupt, 1847 ) locates midway between stoichiometric hematite (Hm...
FIGURES | View All (4)
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The dependence of Fe occupancy on transformation time and temperature (80–1...
Published: 01 September 2023
Figure 4. The dependence of Fe occupancy on transformation time and temperature (80–170 °C) as revealed by a best fit surface to our refined TRXRD data at pH 10. Our refined Fe occupancy data are indicated by black dots. Initial structures for hydrohematite were always highly Fe-deficient
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Fe-O bond length dependence on Fe occupancy, combining the data from the tr...
Published: 01 September 2023
Figure 13. Fe-O bond length dependence on Fe occupancy, combining the data from the transformation of ferrihydrite (Fh) to hydrohematite (Hyhm) at 90 °C and pH 11, hydrohematite to hematite (Hm) from room temperature to 700 °C, and goethite to hematite from 200 to 800 °C ( Gualtieri
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The crystal structure of <span class="search-highlight">hydrohematite</span> synthesized at pH 11 and heated at 9...
Published: 01 September 2023
Figure 6. The crystal structure of hydrohematite synthesized at pH 11 and heated at 90 °C for 1.5 h, with a refined Fe occupancy of 0.84(1). The hydrohematite structure exhibits sheets of oxygen (O) anions that are hexagonal closest packed, and iron (Fe) resides within octahedral sites. Two types
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( a ) A representative refinement at 90 °C and pH 11 showed that hydrohemat...
Published: 01 September 2023
Figure 3. ( a ) A representative refinement at 90 °C and pH 11 showed that hydrohematite (Hyhm, black dots) and goethite (Gt, blue squares) precipitated from ferrihydrite with time. ( b ) Normalized scale factors and ( c ) crystallite sizes achieved a plateau at ~3300 s, indicating
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Refined lattice parameters in the dehydration of <span class="search-highlight">hydrohematite</span> to hematite ...
Published: 01 September 2023
Figure 11. Refined lattice parameters in the dehydration of hydrohematite to hematite with increased temperatures. (Color online.)
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Stacked TRXRD patterns showing the transformation of <span class="search-highlight">hydrohematite</span> to hemat...
Published: 01 September 2023
Figure 8. Stacked TRXRD patterns showing the transformation of hydrohematite to hematite when dry heated from room temperature to 700 °C.
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Crystallographic evolution in the transformation of <span class="search-highlight">hydrohematite</span> to hemati...
Published: 01 September 2023
Figure 10. Crystallographic evolution in the transformation of hydrohematite to hematite with increased temperatures. Standard deviations of refined values are smaller than symbols. (Color online.)
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Changes in refined bond angles during <span class="search-highlight">hydrohematite</span> growth at 90 °C pH 11. ...
Published: 01 September 2023
Figure 7. Changes in refined bond angles during hydrohematite growth at 90 °C pH 11. ( a ) The Fe-O-Fe angle reflects octahedra that are adjacent along the c -axis. These face-sharing octahedra exhibited the greatest expansion (16.65%) of all Fe-O-Fe and O-Fe-O angles. ( b ) The Fe-O-Fe angle
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A comparison of the formation of <span class="search-highlight">hydrohematite</span> from ferrihydrite in our stu...
Published: 01 September 2023
Figure 12. A comparison of the formation of hydrohematite from ferrihydrite in our study ( Chen et al. 2021 ) and hematite formation from akageneite in Peterson et al. (2018) . The variation in Fe occupancy in hematite is shown as a function of final phase abundance (as represented by final
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XRD patterns with varied Fe occupancies during the transformation of hydroh...
Published: 01 September 2023
Figure 9. XRD patterns with varied Fe occupancies during the transformation of hydrohematite to hematite. The ratio of starred peaks at (214) and (300) is sensitive to Fe occupancies. (Color online.)
Journal Article
Published: 01 February 2007
Clays and Clay Minerals (2007) 55 (1): 59–70.
..., studied by means of X-ray diffractometry, Mössbauer spectroscopy and infrared spectroscopy, appeared to involve build-up, then gradual condensation of OH bridges, leading to the conversion of ferrihydrite to hydrohematite with approximately 4 – 5% of residual water. The presence of other solids...
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Intergrowth of natural <span class="search-highlight">hydrohematite</span> (Hyhm) and hydrogoethite (Hygt) from S...
Published: 20 July 2021
Figure 3. Intergrowth of natural hydrohematite (Hyhm) and hydrogoethite (Hygt) from Salisbury, Connecticut, USA (Genth [Genth Collection at The Pennsylvania State University, USA] specimen #255.3). Images show the interface of Hyhm and Hygt as observed by light reflectance microscopy
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Crystallographic evolution of <span class="search-highlight">hydrohematite</span> (Hyhm) formation. (A) Stacked t...
Published: 20 July 2021
Figure 4. Crystallographic evolution of hydrohematite (Hyhm) formation. (A) Stacked time-resolved X-ray diffraction (TRXRD) patterns of transformation of two-line ferrihydrite (Fh, with d -spacings [ d ] at 2.54 Å and 1.46 Å) to Hyhm and goethite (Gt) at 90 °C and pH 11. (B) Rietveld refinement
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Evolution of unit-cell parameters  a  ( a ),  c  ( b ), and volume ( c ) du...
Published: 01 September 2023
Figure 5. Evolution of unit-cell parameters a ( a ), c ( b ), and volume ( c ) during hydrohematite growth at 90 °C pH 11. Changes in Fe occupancy are included ( d ) ( Chen et al. 2021 ) for comparison. Refinement errors, as reported by GSAS, are smaller than symbols. (Color online.)