“…No traces of Fe> could be observed within the statistics of our data. However, unlike previous works with similar samples (5,11,12), our resolution was enough to sort out two octahedrally coordinated sites with different distortions. The linewidths obtained are similar to values reported in previous works on this type of minerals.…”
Section: Resultsmentioning
confidence: 98%
“…This was the criterion also used to fit the unresolved spectrum of the sample measured by Wenger et al (5). Garg et al (11) and Oliveira et al (12) used only one quadrupole signal to fit their data (although synthetic samples were used in Ref. (11)).…”
Section: Resultsmentioning
confidence: 99%
“…Garg et al (11) and Oliveira et al (12) used only one quadrupole signal to fit their data (although synthetic samples were used in Ref. (11)). However, one-doublet fitting proved inadequate in our case (see Figs.…”
“…No traces of Fe> could be observed within the statistics of our data. However, unlike previous works with similar samples (5,11,12), our resolution was enough to sort out two octahedrally coordinated sites with different distortions. The linewidths obtained are similar to values reported in previous works on this type of minerals.…”
Section: Resultsmentioning
confidence: 98%
“…This was the criterion also used to fit the unresolved spectrum of the sample measured by Wenger et al (5). Garg et al (11) and Oliveira et al (12) used only one quadrupole signal to fit their data (although synthetic samples were used in Ref. (11)).…”
Section: Resultsmentioning
confidence: 99%
“…Garg et al (11) and Oliveira et al (12) used only one quadrupole signal to fit their data (although synthetic samples were used in Ref. (11)). However, one-doublet fitting proved inadequate in our case (see Figs.…”
“…They contain two doublets of Fe 3+ and a weak doublet of Fe 2+ at 90 K or Fe 2.5+ at 295 K related to wolframiterelated structures (Table 2). The remaining doublet of Fe 2+ is assigned to columbite-(Fe) (Garg et al, 1991).…”
Section: Mössbauer Spectroscopymentioning
confidence: 99%
“…They contain two doublets of Fe 3+ and a weak doublet of Fe 2+ at 90 K or Fe 2.5+ at 295 K related to wolframite-related structures (Table 2). The remaining doublet of Fe 2+ is assigned to columbite-(Fe) (Garg et al ., 1991). Figure 5.Mössbauer spectra of a mixture of dmitryvarlamovite, a Fe 3+ NbO 4 phase and columbite-(Fe) at (a) room (295 K) temperature and (b) 90 K.…”
The new columbite-supergroup mineral dmitryvarlamovite, ideally Ti2(Fe3+Nb)O8, was discovered in weathered alkaline metasomatic assemblages formed after late Riphaean sedimentary carbonate rocks of the Verkhne-Shchugorskoe deposit, Middle Timan Mts., Russia. The associated minerals are columbite-(Fe), pyrochlore-group minerals, monazite-(Ce), xenotime-(Y), baryte, pyrite, drugmanite and plumbogummite. Dmitryvarlamovite occurs as isolated anhedral equant grains up to 0.5 mm across. The colour of dmitryvarlamovite is black, the streak is black and the lustre is submetallic. The new mineral is brittle, with the mean VHN hardness of 753 kg mm–2 corresponding to the Mohs’ hardness of 6. No cleavage is observed. The fracture is conchoidal. The calculated density is 4.891 g⋅cm–3. In reflected light, dmitryvarlamovite is light grey; no pleochroism is observed. The reflectance values (Rmin, % / Rmax, % / λ, nm) are: 19.8/20.3/470, 18.3/18.9/546, 17.8/18.5/589 and 17.3/17.8/650. The chemical composition is (electron microprobe data, with iron divided into Fe2O3 and FeO based on the charge balance, wt.%): MnO 0.11, FeO 1.51, V2O3 0.89, Cr2O3 0.28, Fe2O3 19.26, TiO2 37.72, Nb2O5 40.08, total 99.85. The IR and Raman spectra indicate the absence of H-, C- and N-bearing groups. The empirical formula is (Fe2+0.08V3+0.05Cr3+0.01Fe3+0.92Ti1.79Nb1.15)Σ4.00O8. The crystal structure was determined using single-crystal X-ray diffraction data and refined to R = 0.048. Dmitryvarlamovite is orthorhombic, space group P21212, a = 4.9825(6), b = 4.6268(4), c = 5.5952(6) Å and V = 5.5952(6) Å3 (Z = 1). The structure is related to those of wolframite-group minerals but differs in the scheme of cation ordering. The crystal-chemical formula derived based on the structural data is (Ti0.57Nb0.21Fe3+0.15Fe2+0.04V0.02Cr0.01)2(Nb0.36Ti0.33Fe3+0.31)2O8. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.58 (40) (011), 2.911 (100) (111), 2.809 (40) (002), 2.497 (38) (020), 2.447 (29) (103), 1.7363 (32) (103) and 1.7047 (29) (220). Dmitryvarlamovite is named after Dmitry Anatol'evich Varlamov (b. 1965).
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