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| Formula: |
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| System: | Orthorhombic | |||||||||||||||
| Dimorph of: | Chromite | |||||||||||||||
Spinel group. High pressure polymorph of chromite. Abstract (from Chen, et al, 2003): The first natural occurrence of a high-pressure polymorph of chromite has been discovered in the shock-metamorphosed Suizhou meteorite. The composition of this high-pressure polymorph is identical to that of the precursor chromite. The Raman spectrum of this polymorph is distinct from that of chromite. Synchrotron X-ray diffraction analysis revealed that this polymorph has an orthorhombic CaTi2O4-type structure. The cell parameters are: a = 9.462(6) Å, b = 9.562(9) Å, c = 2.916(1) Å, V = 263.8(4) Å3 (Z=4), space group = Bbmm, and the density = 5.63 g/cm3 (the numbers in parentheses are standard deviations on the last significant digits). This polymorph is 11.5% denser than chromite. The P-T conditions for the phase transformation from chromite to the CaTi2O4-structured polymorph are estimated at 20–23 GPa and 1800 to 2000 °C, respectively. This dense CaTi2O4-structured FeCr2O4 phase could be a host phase for Cr, Al, Fe, Mg and Mn and other metallic elements in the deep Earth. | ||||||||||||||||
Classification of Xieite | ||||||||||||||
| IMA status: | Approved 2007 | |||||||||||||
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| Nickel-Strunz 10th (pending) edition ID: | 4.B0. 4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates) B : Metal: Oxygen = 3:4 and similar 0 : | |||||||||||||
| mindat.org URL: | http://www.mindat.org/min-35792.html Please feel free to link to this page. | |||||||||||||
Type Occurrence of Xieite | ||||||||||||||
| Type Locality: | Suizhou meteorite (Suizhou L6 chondrite), Dayanpo, Zengdu District, Suizhou Prefecture, Hubei Province, China | |||||||||||||
| Geological Setting of type material: | L6 chondrite meteorite | |||||||||||||
Crystallography of Xieite | ||||||||||||||
| Crystal System: | Orthorhombic | |||||||||||||
| Cell Parameters: | a = 9.462Å, b = 9.562Å, c = 2.916Å | |||||||||||||
| Ratio: | a:b:c = 0.99 : 1 : 0.305 | |||||||||||||
| Unit Cell Volume: | V 263.83 ų (Calculated from Unit Cell) | |||||||||||||
Chemical Properties of Xieite | ||||||||||||||
| Formula: |
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| Essential elements: | ||||||||||||||
| All elements listed in formula: | Cr, Fe, O | |||||||||||||
| Empirical Formula: |
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Other Names for Xieite | ||||||||||||||
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Other Information | ||||||||||||||
| Health Warning: | No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care. | |||||||||||||
References for Xieite | ||||||||||||||
| Reference List: | Chen, M., Shu, J., Xie, X., Mao, H. (2003): Natural CaTi2O4-structured FeCr2O4 polymorph in the Suizhou meteorite and its significance in mantle mineralogy. Geochimica et Cosmochimica Acta, 67, 3937-3942. Chen, M., Shu, J., Mao, H., Xie, X., Hemley, R.J. (2003): Natural occurrence and synthesis of two new postspinel polymorphs of chromite. Proceedings of the National Academy of Science USA, 100, 14651-14654. | |||||||||||||
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