Geological setting and mineral composition of (apatite)-nepheline-titanite ore from the Khibiny massif enable selective mining of titanite ore, and its processing with sulfuric-acid method, without preliminary concentration in flotation cells. In this process flow diagram, titanite losses are reduced by an order of magnitude in comparison with a conventional flotation technology. Further, dissolution of titanite in concentrated sulfuric acid produces titanyl sulfate, which, in turn, is a precursor for titanosilicate synthesis. In particular, synthetic analogues of the ivanyukite group minerals, SIV, was synthesized with hydrothermal method from the composition based on titanyl-sulfate, and assayed as a selective cation-exchanger for Cs and Sr.

At present, the vesuvianite group of minerals consists of eight members, six of which are distinguished by the dominant cation in the Y1(A,B) five-coordinated site. We investigated two vesuvianite samples from the type locality by electron microprobe analysis, Mössbauer and infrared spectroscopy, TGA/DSC, MAS NMR, single-crystal and powder X-ray diffraction. The crystal structures of these samples (# 27844 and 51062 from the Vesuvius collection, Fersman Mineralogical Museum, Moscow) have been refined to R₁ = 0.027 and R₁ = 0.035, respectively. Both samples have the space group P4/nnc; a = 15.5720(3) and 15.5459(3), c = 11.8158(5) and 11.7988(4), respectively. In both samples low-occupied T1 and T2 sites are populated by minor B and Al, which agrees with their high-temperature origin. According to our experimental results, the general revised crystal-chemical formula of vesuvianite can be written as ^VII−IXX₁₉^VY₁^VIY₁₂(Z₂O₇)₄(ZO₄)₁₀(W)₁₀, where X are seven- to nine-coordinated sites of Ca with minor Na, K, Fe²⁺ and REE impurities; ^VY has a square pyramidal coordination and is occupied predominantly by Fe³⁺ with subordinate Mg, Al, Fe²⁺ and Cu²⁺; ^VIY has octahedral coordination and is predominantly occupied by Al with subordinate Mg, Fe²⁺, Fe³⁺, Mn²⁺, Mn³⁺, Ti, Cr and Zn; ZO₄ = SiO₄, sometimes with subordinate AlO₄ and/or (OH)₄, and W = OH, F, with minor O and Cl. The idealized charge-balanced formula of the vesuvianite end-member without subordinate cations is Ca₁₉Fe³⁺(Al₁₀Me²⁺₂)(Si₂O₇)₄(SiO₄)₁₀O(OH)₉, where Ме = Fe²⁺, Mg²⁺, Mn²⁺.

Chirvinskyite, (Na,Ca)₁₃(Fe,Mn,□)₂(Ti,Nb)₂(Zr,Ti)₃(Si₂O₇)₄(OH,O,F)₁₂, is a new wöhlerite–related zirconotitano–sorosilicate. It is triclinic, P $\overline{1}$ , a = 7.0477(5), b = 9.8725(5), c = 12.2204(9) Å, α = 77.995(5), β = 82.057(6), γ = 89.988(5)°, V = 823.35(9) ų, Z = 1. The mineral was found in albitized alkaline pegmatites in a foyaite of the Mt. Takhtarvumchorr (Khibiny alkaline massif, Kola Peninsula, Russia, N 67°40′, E 33°33′). Chirvinskyite forms sheaf–like and radiated aggregates (up to 6 mm in diameter) of split fibrous crystals hosted by saccharoidal fluorapatite and albite. The mineral is pale cream in color, with a silky luster and a white streak. The cleavage is not recognized. Mohs hardness is 5. Chirvinskyite is biaxial (–), α 1.670(2), β 1.690(2), γ 1.705(2) (589 nm), 2V_calc = 80.9°. The calculated and measured densities are 3.41 and 3.07(2) g·cm⁻³, respectively. The empirical formula based on Si = 8 apfu is (Na_9.81Ca_3.28K_0.01)_∑13.10(Fe_0.72Mn_0.69□_0.54Mg_0.05)_∑2.00 (Ti_1.81Nb_0.19)_∑2.00(Zr_2.27Ti_0.63)_∑2.90(Si₂O₇)₄{(OH)_5.94O_3.09F_2.97}_∑12.00. Chirvinskyite belongs to a new structure type of minerals and inorganic compounds and is related to the wöhlerite-group minerals. Its modular “wallpaper” structure consists of disilicate groups Si₂O₇ and three types of “octahedral walls”. The mineral is named in honor of Petr Nikolaevich Chirvinsky (1880–1955), Russian geologist and petrographer, head of the Petrography Department of the Perm’ State University (1943–1953), for his contributions to mineralogy and petrology, including studies of the Khibiny alkaline massif.