Abstract
A natural barioferrite, BaFe3+12O19, from a larnite–schorlomite–gehlenite vein of paralava within gehlenite hornfels of the Hatrurim Complex at Har Parsa, Negev Desert, Israel, was investigated by Raman spectroscopy, electron probe microanalysis, and single-crystal X-ray analyses acquired over the temperature range of 100–400 K. The crystals are up to 0.3 mm × 0.1 mm in size and form intergrowths with hematite, magnesioferrite, khesinite, and harmunite. The empirical formula of the barioferrite investigated is as follows: (Ba0.85Ca0.12Sr0.03)∑1(Fe3+10.72Al0.46Ti4+0.41Mg0.15Cu2+0.09Ca0.08Zn0.04Mn2+0.03Si0.01)∑11.99O19. The strongest bands in the Raman spectrum are as follows: 712, 682, 617, 515, 406, and 328 cm−1. The structure of natural barioferrite (P63/mmc, a = 5.8901(2) Å, c = 23.1235(6) Å, V = 694.75(4) Å3, Z = 2) is identical with the structure of synthetic barium ferrite and can be described as an interstratification of two fundamental blocks: spinel-like S-modules with a cubic stacking sequence and R-modules that have hexagonal stacking. The displacement ellipsoids of the trigonal bipyramidal site show elongation along the [001] direction during heating. As a function of temperature, the mean apical Fe–O bond lengths increase, whereas the equatorial bond lengths decrease, which indicates dynamic disorder at the Fe2 site.
Highlights
Barioferrite, BaFe12 O19, P63 /mmc, a = 5.8921(2) Å, c = 23.1092(8) Å was described as a new mineral species from a metamorphosed baryte nodule, which was found on the southern slope of
We present the results of the single-crystal structural investigation of natural barioferrite for the first time
The barioferrite investigated was found in the outcrops at Har Parsa, which is located in the eastern part of the Hatrurim Basin, about 10 km southeast of Arad, Negev Desert, Israel
Summary
Har Ye’elim, a mountain in the Negev Desert, Israel In this nodule, barioferrite occurs as small platy crystals up to 3 × 15 × 15 μm , as well as their aggregates. There are several descriptions of synthetic BaFe12 O19 [2,3,4,5], whereas there are no previous single-crystal structure studies of natural BaFe12 O19. Many authors have tried to refine the crystal structure of synthetic BaFe12 O19 in different space groups We pay attention to the structural deformations of the trigonal bipyramidal site at different temperatures and consider mechanisms for the incorporation of Al, Ti, and Mg into the structure of natural barioferrite
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