Yuanfuliite crystals, ideally MgFe3+O(BO3), i.e. the Fe3+ analogue of warwickite Mg1.5Ti0.5O(BO3), have been found in ultramafic rocks of Precambrian age in Inglefield Land (North-West Greenland). Structure refinements (space group Pnma) of two crystals with slightly different composition (agreement factors R = 0.023 and 0.025, respectively), have shown, in both cases, that the two octahedral M1 and M2 sites are geometrically quite similar but compositionally different, being Fe3+ strongly ordered at M1 and Al partially ordered at M2. The yuanfuliite cation ordering scheme has been compared with that of warwickite. Selected area electron diffraction patterns and high-resolution transmission electron microscopy images of yuanfuliite show a generally well-ordered structure. Some defects, confined to small crystal areas, are related to regularly distributed dislocations.
Crystal structure and chemistry of yuanfuliite and its relationships with warwickite / P. W. U., Appel; Bigi, Simona; Brigatti, Maria Franca. - In: EUROPEAN JOURNAL OF MINERALOGY. - ISSN 0935-1221. - STAMPA. - 11:(1999), pp. 483-491.
Crystal structure and chemistry of yuanfuliite and its relationships with warwickite
BIGI, Simona;BRIGATTI, Maria Franca
1999
Abstract
Yuanfuliite crystals, ideally MgFe3+O(BO3), i.e. the Fe3+ analogue of warwickite Mg1.5Ti0.5O(BO3), have been found in ultramafic rocks of Precambrian age in Inglefield Land (North-West Greenland). Structure refinements (space group Pnma) of two crystals with slightly different composition (agreement factors R = 0.023 and 0.025, respectively), have shown, in both cases, that the two octahedral M1 and M2 sites are geometrically quite similar but compositionally different, being Fe3+ strongly ordered at M1 and Al partially ordered at M2. The yuanfuliite cation ordering scheme has been compared with that of warwickite. Selected area electron diffraction patterns and high-resolution transmission electron microscopy images of yuanfuliite show a generally well-ordered structure. Some defects, confined to small crystal areas, are related to regularly distributed dislocations.
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