Hydrothermal Single Crystal Growth and Structural Investigation of the Nepheline and Kalsilite Stuffed Tridymite Species

Terry, Rylan J.; McMillen, Colin D.; Kolis, Joseph W.

doi:10.1007/s10870-022-00940-6

Cited by 3 publications

(2 citation statements)

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“…The crystal structures of the studied samples are generally similar to the previously studied ones with the space group P6 3 [17,18,24,[54][55][56][57] (Figure 6). 4.…”

Section: Crystal Structure Of the Nephelinesupporting

confidence: 76%

Iron in Nepheline: Crystal Chemical Features and Petrological Applications

et al. 2022

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Nepheline is a nominally anhydrous aluminosilicate that typically contains an impurity of ferric iron replacing aluminum in tetrahedral sites. However, previous researchers noted the constant presence of ferrous iron in the chemical composition of nepheline from the rocks of the Khibiny and Lovozero massifs (Kola Peninsula, Russia). We have carried out microprobe, spectroscopic, chemical and crystal chemical studies of nepheline from the Lovozero massif. We have established the presence of molecular water in nepheline, and also that the incorporation of ferrous iron into nepheline crystal structure is associated with the simultaneous increasing of the coordination number from four to five (or six) due to the inclusion of the ‘additional’ water molecules that form point [FeO4(H2O)n]-defects (where n = 1,2) in the tetrahedral framework. The nepheline iron content is closely related to the presence of small needle-like aegirine inclusions. The total iron content in nepheline saturated with aegirine needles is approximately an order of magnitude lower than in nepheline free from aegirine inclusions. Most likely the aegirine inclusions in nepheline are formed as a result of the decomposition of the nepheline–“iron nepheline” solid solution. We propose that this process is triggered by the oxidation of ferrous iron in the crystal structure of nepheline.

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“…The crystal structures of the studied samples are generally similar to the previously studied ones with the space group P6 3 [17,18,24,[54][55][56][57] (Figure 6). 4.…”

Section: Crystal Structure Of the Nephelinesupporting

confidence: 76%

Iron in Nepheline: Crystal Chemical Features and Petrological Applications

et al. 2022

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“…Typically, the Ca and Al sites are heavily substituted with a wide range of other ions, notably iron and magnesium. We have previously had good success in employing high temperature hydrothermal conditions (500-700 • C) in preparing a wide range of mineralogically inspired materials as high quality single crystals [18][19][20][21]. In our attempts to prepare grossular single crystals (garnet, Ca 3 Al 2 Si 3 O 12 ) in high temperature hydrothermal systems, we sometimes observed vesuvianite accompanied by the grossular formation.…”

Section: Introductionmentioning

confidence: 98%

Hydrothermal Synthesis and Crystal Structure of Vesuvianite Compounds, Ca19Al13Si18O71(OH)7 and Sr19Fe12Ge19O72(OH)6

et al. 2023

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New compositions of synthetic vesuvianite were investigated using hydrothermal synthesis. High quality single crystals with the formula Ca19Al13Si18O71(OH)7 (I) having the vesuvianite-type structure were crystallized during a high temperature hydrothermal growth reaction. Starting materials of Al2O3 and CaSiO3 reacted at 670 °C and 2 kbar in 0.5 M aqueous alkali hydroxide mineralizer to form single crystals up to 0.25 mm per edge. Similar reactions employing SrO, Fe2O3, and GeO2 reacting at 580 °C and 2 kbar in 6 M aqueous alkali hydroxide mineralizers led to the formation of the analogous Sr19Fe12Ge19O72(OH)6 (II). These crystals were obtained in sizes up to 0.5 mm per edge. The structures of both compounds were refined in space group P4/nnc after careful evaluation of the diffraction data and subsequent test refinements. Elemental analysis indicated only the presence of Ca2+, Al3+, and Si4+ cations in I and only the presence of Sr2+, Fe3+, and Ge4+ cations in II, representing synthetic vesuvianite comprising the minimum number of unique cations. The use of larger cations than are typically found in natural vesuvianite, such as Sr2+, Fe3+, and Ge4+, resulted in an expanded crystalline lattice and extended the vesuvianite analogs to include an increasing variety of elements.

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