ALBERT

Description: The crystal structure of betalomonosovite, ideally Na 6 4 Ti 4 (Si 2 O 7 ) 2 [PO 3 (OH)][PO 2 (OH) 2 ]O 2 (OF), a 5.3331(7), b 14.172(2), c 14.509(2) Å, α 103.174(2), β 96.320(2), 90.278(2)°, V 1060.7(4) Å 3 , from the Lovozero alkaline massif, Kola peninsula, Russia, has been refined in the space group P 1{macron} to R = 6.64% using 3379 observed ( F o 〉 4 F ) reflections collected with a single-crystal APEX II ULTRA three-circle diffractometer with a rotating-anode generator (Mo K α), multilayer optics, and an APEX-II 4K CCD detector. Electron-microprobe analysis gave the empirical formula (Na 5.39 Ca 0.36 Mn 0.04 Mg 0.01 ) 5.80 (Ti 2.77 Nb 0.48 Mg 0.29 Fe 3+ 0.23 Mn 0.20 Zr 0.02 Ta 0.01 ) 4 (Si 2.06 O 7 ) 2 [P 1.98 O 5 (OH) 3 ]O 2 [O 0.82 F 0.65 (OH) 0.53 ] 2 , D calc. = 2.969 g cm –3 , Z = 2, calculated on the basis of 26 (O + F) apfu , with H 2 O determined from structure refinement. The crystal structure of betalomonosovite is characterized by extensive cation and anion disorder: more than 50% of cation sites are partly occupied. The crystal structure of betalomonosovite is a combination of a titanium silicate (TS) block and an intermediate ( I ) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral) and exhibits linkage and stereochemistry typical for Group IV (Ti + Mg + Mn = 4 apfu ) of the TS-block minerals. The I block is a framework of Na polyhedra and P tetrahedra which ideally gives {Na 2 4 [PO 3 (OH)][PO 2 (OH) 2 ]} pfu . Betalomonosovite is an Na-poor OH-bearing analogue of lomonosovite, Na 10 Ti 4 (Si 2 O 7 ) 2 (PO 4 ) 2 O 4 . In the betalomonosovite structure, there is less Na in the I block and in the TS block when compared to the lomonosovite structure. The OH groups occur mainly in the I block where they coordinate P and Na atoms and in the O sheet of the TS block (minor). The presence of OH groups in the I block and in the TS block is supported by IR spectroscopy and bond-valence calculations on anions. High-resolution TEM of lomonosovite shows the presence of pervasive microstructural intergrowths, accounting for the presence of signals from H 2 O in the infrared spectrum of anhydrous lomonosovite. More extensive lamellae in betalomonosovite suggest a topotactic reaction from lomonosovite to betalomonosovite.

Description: 〈span〉〈div〉Abstract〈/div〉The crystal structure of polylithionite-1〈span〉M〈/span〉 from Darai-Pioz, (K〈sub〉0.97〈/sub〉Na〈sub〉0.03〈/sub〉Rb〈sub〉0.01〈/sub〉)〈sub〉Σ1.01〈/sub〉(Li〈sub〉2.04〈/sub〉Al〈sub〉0.84〈/sub〉 Ti〈sup〉4+〈/sup〉〈sub〉0.09〈/sub〉Fe〈sup〉3+〈/sup〉〈sub〉0.03〈/sub〉)〈sub〉Σ3.00〈/sub〉(Si〈sub〉3.98〈/sub〉Al〈sub〉0.02〈/sub〉)O〈sub〉10〈/sub〉[F〈sub〉1.68〈/sub〉(OH)〈sub〉0.33〈/sub〉]〈sub〉Σ2〈/sub〉, 〈span〉a〈/span〉 5.1974(4), 〈span〉b〈/span〉 8.9753(6), 〈span〉c〈/span〉 10.0556(7) Å, β 100.454(1)°, 〈span〉V〈/span〉 461.30(6) Å〈sup〉3〈/sup〉, space group 〈span〉C〈/span〉2, 〈span〉Z〈/span〉 = 2, was refined to 〈span〉R〈/span〉〈sub〉1〈/sub〉 = 1.99% using Mo〈span〉K〈/span〉α X-radiation. In the space group 〈span〉C〈/span〉2, there are three octahedrally coordinated 〈span〉M〈/span〉 sites in the 1〈span〉M〈/span〉 mica structure: the 〈span〉M〈/span〉(1) site is occupied by Li〈sup〉+〈/sup〉 and minor vacancy that is likely locally associated with Ti〈sup〉4+〈/sup〉 at the 〈span〉M〈/span〉(2) site; the 〈span〉M〈/span〉(2) site is occupied dominantly by Al〈sup〉3+〈/sup〉, with other minor divalent to tetravalent cations; the 〈span〉M〈/span〉(3) site is completely occupied by Li〈sup〉+〈/sup〉. In the space group 〈span〉C〈/span〉2, the structure is completely ordered. Each non-bridging O〈sup〉2–〈/sup〉 ion is surrounded by an ordered arrangement of 2Li〈sup〉+〈/sup〉 + Al〈sup〉3+〈/sup〉 + Si〈sup〉4+〈/sup〉 with an incident bond-valence sum of 1.95 〈span〉vu〈/span〉 (valence units). The F〈sup〉–〈/sup〉 ion is coordinated by Li〈sup〉+〈/sup〉 + Li〈sup〉+〈/sup〉 + Al〈sup〉3+〈/sup〉 with an incident bond-valence sum of 0.84 〈span〉vu〈/span〉 (values around F〈sup〉–〈/sup〉 generally tend to be lower than ideal). Thus, the valence-sum rule is satisfied, both long range and short range. In the space group 〈span〉C〈/span〉2/〈span〉m〈/span〉, there is long-range order but not short-range order. There are three different short-range arrangements, one of which has bond-valence deficiencies of 0.38 and 0.49 〈span〉vu〈/span〉 around the non-bridging O〈sup〉2–〈/sup〉 ion and the F〈sup〉–〈/sup〉 ion, destabilizing the structure relative to the more ordered arrangement of the 〈span〉C〈/span〉2 structure, which conforms more closely to the valence-sum rule. The drive to lower the symmetry in polylithionite-1〈span〉M〈/span〉 from 〈span〉C〈/span〉2/〈span〉m〈/span〉 to 〈span〉C〈/span〉2 comes from the short-range bond-valence requirements of the structure.〈/span〉

Description: A bstract Saamite, BaTiNbNa 3 Ti(Si 2 O 7 ) 2 O 2 (OH) 2 (H 2 O) 2 , is a Group-III TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as transparent platy crystals 2–10 μm thick and up to 180 μm across. It is colorless to very pale tan, with a white streak and a vitreous luster. The mineral formed in a pegmatite as a result of hydrothermal activity. Associated minerals are natrolite, barytolamprophyllite, kazanskyite, nechelyustovite, hydroxylapatite, belovite-(La), belovite-(Ce), gaidonnayite, nenadkevichite, epididymite, apophyllite-(KF), and sphalerite. Saamite has perfect cleavage on {001}, uneven fracture and a Mohs hardness ca. 3. Its calculated density is 3.243 g/cm 3 . Saamite is biaxial positive with α 1.760, β 1.770, 1.795 ( 589 nm), 2 V meas. = 69(2)°, 2 V calc. = 65°, with medium dispersion, r 〉 v . It is nonpleochroic. Saamite is triclinic, space group P 1 {macron} , a 5.437(2), b 7.141(3), c 21.69(1) Å, α 92.97(1), β 96.07(1), 90.01(1)°, V 836.3(11) Å 3 . The strongest lines in the X-ray powder-diffraction pattern [ d (Å)(I)( hkl )] are: 21.539(100)(001), 2.790(15)(122), 2.692(14)(008), 3.077(13)(007), 7.180(11)(003), 2.865(11)(1 2 {macron} 2), 1.785(9)(1 1 {macron} 4), 2.887(9)( 1 {macron} 22, 0 1 {macron} 7, 115), and 1.785(9)(0 4 {macron} 1, 1 3 {macron} 7, 040, 2 {macron} 2 {macron} 8, 230, 23 1 {macron} ). Chemical analysis by electron microprobe gave Nb 2 O 5 12.24, TiO 2 20.37, SiO 2 29.07, Al 2 O 3 0.08, FeO 0.32, MnO 5.87, MgO 0.04, BaO 11.31, SrO 2.51, CaO 1.76, K 2 O 0.77, Na 2 O 8.39, H 2 O 5.77, F 1.71, O = F –0.72, sum 99.49 wt.%; H 2 O was determined from structure refinement and its presence was confirmed by IR spectroscopy. The empirical formula based on 20 (O + F) atoms pfu is (Ba 0.61 Sr 0.20 K 0.13 0.06 ) 1 ( 0.74 Ca 0.26 ) 1 ( Na 2.22 Mn 0.55 Fe 0.04 2 + 0.19 ) 3 (Ti 2.09 Nb 0.76 Mn 0.13 Mg 0.01 Al 0.01 ) 3 Si 3.97 O 19.26 H 5.26 F 0.74 , Z = 2. The simplified formula is as follows: Ba(,Ca)Ti(Nb,Ti)(Na,Mn) 3 (Ti,Nb)(Si 2 O 7 ) 2 O 2 (OH,F) 2 (H 2 O) 2 . The IR spectrum of saamite contains the following bands: ~1605, 1645, ~1747 and ~3420 cm –1 . The crystal structure was solved by direct methods and refined to an R 1 index of 9.92%. In the crystal structure of saamite, the main structural unit is the TS block, which consists of HOH sheets (H-heteropolyhedral, O-octahedral). The TS block exhibits linkage and stereochemistry typical for Group III [Ti (+ Nb + Mg) = 3 apfu ] of TS-block minerals. The O sheet is composed of Na- and Ti-dominant octahedra and has ideal composition Na 3 Ti apfu . The TS block has two different H sheets where Si 2 O 7 groups link to [5]-coordinated Ti and [6]-coordinated Nb polyhedra, respectively. There are two peripheral sites, [10]-coordinated A P (1) and [8]-coordinated A P (2), occupied mainly by Ba (less Sr and K) at 94% and Ca at 26%, respectively. In the crystal structure of saamite, adjacent TS blocks connect in two different ways: (1) via hydrogen bonds between H 2 O–H 2 O groups and H 2 O–O atoms of adjacent TS blocks; (2) via a layer of Ba atoms that constitute the I block. The TS block, I block and types of self-linkage of TS blocks are topologically identical to those in the nechelyustovite structure. The mineral is named after the Saami (Caam in Cyrillic) indigenous people who inhabit parts of the Kola Peninsula of Russia, far northern Norway, Sweden, and Finland.

Description: 〈span〉〈div〉Abstract〈/div〉The crystal structure of polylithionite-1〈span〉M〈/span〉 from Darai-Pioz, (K〈sub〉0.97〈/sub〉Na〈sub〉0.03〈/sub〉Rb〈sub〉0.01〈/sub〉)〈sub〉Σ1.01〈/sub〉(Li〈sub〉2.04〈/sub〉Al〈sub〉0.84〈/sub〉 Ti〈sup〉4+〈/sup〉〈sub〉0.09〈/sub〉Fe〈sup〉3+〈/sup〉〈sub〉0.03〈/sub〉)〈sub〉Σ3.00〈/sub〉(Si〈sub〉3.98〈/sub〉Al〈sub〉0.02〈/sub〉)O〈sub〉10〈/sub〉[F〈sub〉1.68〈/sub〉(OH)〈sub〉0.33〈/sub〉]〈sub〉Σ2〈/sub〉, 〈span〉a〈/span〉 5.1974(4), 〈span〉b〈/span〉 8.9753(6), 〈span〉c〈/span〉 10.0556(7) Å, β 100.454(1)°, 〈span〉V〈/span〉 461.30(6) Å〈sup〉3〈/sup〉, space group 〈span〉C〈/span〉2, 〈span〉Z〈/span〉 = 2, was refined to 〈span〉R〈/span〉〈sub〉1〈/sub〉 = 1.99% using Mo〈span〉K〈/span〉α X-radiation. In the space group 〈span〉C〈/span〉2, there are three octahedrally coordinated 〈span〉M〈/span〉 sites in the 1〈span〉M〈/span〉 mica structure: the 〈span〉M〈/span〉(1) site is occupied by Li〈sup〉+〈/sup〉 and minor vacancy that is likely locally associated with Ti〈sup〉4+〈/sup〉 at the 〈span〉M〈/span〉(2) site; the 〈span〉M〈/span〉(2) site is occupied dominantly by Al〈sup〉3+〈/sup〉, with other minor divalent to tetravalent cations; the 〈span〉M〈/span〉(3) site is completely occupied by Li〈sup〉+〈/sup〉. In the space group 〈span〉C〈/span〉2, the structure is completely ordered. Each non-bridging O〈sup〉2–〈/sup〉 ion is surrounded by an ordered arrangement of 2Li〈sup〉+〈/sup〉 + Al〈sup〉3+〈/sup〉 + Si〈sup〉4+〈/sup〉 with an incident bond-valence sum of 1.95 〈span〉vu〈/span〉 (valence units). The F〈sup〉–〈/sup〉 ion is coordinated by Li〈sup〉+〈/sup〉 + Li〈sup〉+〈/sup〉 + Al〈sup〉3+〈/sup〉 with an incident bond-valence sum of 0.84 〈span〉vu〈/span〉 (values around F〈sup〉–〈/sup〉 generally tend to be lower than ideal). Thus, the valence-sum rule is satisfied, both long range and short range. In the space group 〈span〉C〈/span〉2/〈span〉m〈/span〉, there is long-range order but not short-range order. There are three different short-range arrangements, one of which has bond-valence deficiencies of 0.38 and 0.49 〈span〉vu〈/span〉 around the non-bridging O〈sup〉2–〈/sup〉 ion and the F〈sup〉–〈/sup〉 ion, destabilizing the structure relative to the more ordered arrangement of the 〈span〉C〈/span〉2 structure, which conforms more closely to the valence-sum rule. The drive to lower the symmetry in polylithionite-1〈span〉M〈/span〉 from 〈span〉C〈/span〉2/〈span〉m〈/span〉 to 〈span〉C〈/span〉2 comes from the short-range bond-valence requirements of the structure.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Laverovite (IMA 2017-009b), ideally K〈sub〉2〈/sub〉NaMn〈sub〉7〈/sub〉Zr〈sub〉2〈/sub〉(Si〈sub〉4〈/sub〉O〈sub〉12〈/sub〉)〈sub〉2〈/sub〉O〈sub〉2〈/sub〉(OH)〈sub〉4〈/sub〉F, is a kupletskite-group (astrophyllite-supergroup) mineral from Mont Saint-Hilaire, Québec, Canada. Associated minerals are zircophyllite, kupletskite, astrophyllite, aegirine, analcime, orthoclase, and albite. Laverovite is brown, transparent in thin grains, and has a vitreous luster. Mohs hardness is 3, 〈span〉D〈/span〉〈sub〉calc.〈/sub〉 = 3.367 g/cm〈sup〉3〈/sup〉. Laverovite is biaxial (–) with refractive indices (λ = 589 nm) α = 1.670(2), β = 1.710(5), γ = 1.740(5); 2〈span〉V〈/span〉〈sub〉meas.〈/sub〉 = 82(2)°, 2〈span〉V〈/span〉〈sub〉calc.〈/sub〉 = 80°, strong dispersion: 〈span〉r〈/span〉 〉 〈span〉v〈/span〉. Cleavage is perfect parallel to {001}. Chemical analysis by electron microprobe gave Nb〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 0.56, ZrO〈sub〉2〈/sub〉 9.78, TiO〈sub〉2〈/sub〉 4.69, SiO〈sub〉2〈/sub〉 33.52, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 0.94, SrO 0.13, ZnO 0.07, FeO 13.94, MnO 20.51, CaO 0.48, MgO 0.76, Cs〈sub〉2〈/sub〉O 0.05, K〈sub〉2〈/sub〉O 6.00, Na〈sub〉2〈/sub〉O 2.28, F 1.80, H〈sub〉2〈/sub〉O〈sub〉calc.〈/sub〉 2.57, sum 97.32 wt.%; H〈sub〉2〈/sub〉O was calculated from crystal-structure analysis. The empirical formula based on 31.15 (O + F) 〈span〉apfu〈/span〉 with [OH + F = 5 〈span〉pfu〈/span〉 and H〈sub〉2〈/sub〉O = 0.15 〈span〉pfu〈/span〉] is (K〈sub〉1.78〈/sub〉Sr〈sub〉0.02〈/sub〉Cs〈sub〉0.01〈/sub〉□〈sub〉0.19〈/sub〉)〈sub〉Σ2〈/sub〉(□〈sub〉1.85〈/sub〉Na〈sub〉0.15〈/sub〉)〈sub〉Σ2〈/sub〉(Na〈sub〉0.88〈/sub〉Ca〈sub〉0.12〈/sub〉)〈sub〉Σ1〈/sub〉(Mn〈sub〉4.03〈/sub〉Fe〈sup〉2+〈/sup〉〈sub〉2.71〈/sub〉Mg〈sub〉0.25〈/sub〉Zn〈sub〉0.01〈/sub〉)〈sub〉Σ7〈/sub〉(Zr〈sub〉1.11〈/sub〉Ti〈sub〉0.82〈/sub〉Nb〈sub〉0.06〈/sub〉Mg〈sub〉0.01〈/sub〉)〈sub〉Σ2〈/sub〉[(Si〈sub〉7.78〈/sub〉Al〈sub〉0.26〈/sub〉)〈sub〉Σ8.04〈/sub〉O〈sub〉24〈/sub〉]O〈sub〉2〈/sub〉[(OH)〈sub〉3.68〈/sub〉F〈sub〉0.32〈/sub〉]〈sub〉Σ4〈/sub〉F[□〈sub〉1.85〈/sub〉(H〈sub〉2〈/sub〉O)〈sub〉0.15〈/sub〉]〈sub〉Σ2〈/sub〉, 〈span〉Z〈/span〉 = 1. The simplified formula is K〈sub〉2〈/sub〉Na(Mn,Fe〈sup〉2+〈/sup〉)〈sub〉7〈/sub〉(Zr,Ti)〈sub〉2〈/sub〉(Si〈sub〉4〈/sub〉O〈sub〉12〈/sub〉)〈sub〉2〈/sub〉O〈sub〉2〈/sub〉 (OH)〈sub〉4〈/sub〉F. Laverovite is triclinic, space group 〈span〉P〈/span〉, 〈span〉a〈/span〉 5.4329(1), 〈span〉b〈/span〉 11.9232(3), 〈span〉c〈/span〉 11.7491(3) Å, α 112.905(2), β 94.696(1), γ 103.178(1)°, 〈span〉V〈/span〉 670.14(5) Å〈sup〉3〈/sup〉. The six strongest lines in the X-ray powder diffraction data [〈span〉d〈/span〉 (Å)(I)(〈span〉hkl〈/span〉)] are: 3.452(92)(003,111); 2.788(97); 2.680(68); 2.589(100); 2.504(44), and 1.590(50). The crystal structure has been refined to 〈span〉R〈/span〉〈sub〉1〈/sub〉 = 3.26% for 3757 observed (〈span〉F〈/span〉〈sub〉o〈/sub〉 〉 4σ〈span〉F〈/span〉) reflections. In the crystal structure of laverovite, there are four 〈sup〉[4]〈/sup〉〈span〉T〈/span〉 sites, with 〈T–O〉 = 1.621 Å, occupied mainly by Si, with minor Al. TO〈sub〉4〈/sub〉 tetrahedra constitute the T〈sub〉4〈/sub〉O〈sub〉12〈/sub〉 astrophyllite ribbon. The Zr-dominant 〈sup〉[6]〈/sup〉〈span〉D〈/span〉 site is occupied mainly by Zr and Ti and minor Nb and Mg, with 〈D–φ〉 = 2.002 Å (φ = O, F). The T〈sub〉4〈/sub〉O〈sub〉12〈/sub〉 astrophyllite ribbons and D octahedra constitute the H (Heteropolyhedral) sheet. In the O (Octahedral) sheet, there are four Mn〈sup〉2+〈/sup〉-dominant 〈sup〉[6]〈/sup〉〈span〉M〈/span〉(1–4) sites, with 〈M(1–4)–φ〉 = 2.187, 2.174, 2.161, and 2.146 Å (φ = O, OH). Two H sheets and the central O sheet form the HOH block, and adjacent HOH blocks link 〈span〉via〈/span〉 a common X〈span〉P〈/span〉〈sub〉D〈/sub〉 anion of two D octahedra. In the 〈strong〉I〈/strong〉 (Intermediate) block between adjacent HOH blocks, there are two interstitial cation sites, 〈span〉A〈/span〉 and 〈span〉B〈/span〉, and a 〈span〉W〈/span〉〈sub〉A〈/sub〉 site, partly occupied by H〈sub〉2〈/sub〉O. The 〈span〉A〈/span〉 site splits into two partly occupied sites, 〈sup〉[13]〈/sup〉〈span〉A〈/span〉(1) and 〈sup〉[6]〈/sup〉〈span〉A〈/span〉(2), with A(1)–A(2) = 1.108 Å. The 〈sup〉[13]〈/sup〉〈span〉A〈/span〉(1) site is occupied at 90.5%: mainly by K, with minor Sr and Cs, 〈A(1)–φ〉 = 3.326 Å; the 〈sup〉[6]〈/sup〉〈span〉A〈/span〉(2) site is occupied at 7.5% by Na: [□〈sub〉1.85〈/sub〉Na〈sub〉0.15〈/sub〉], 〈A(2)–φ〉 = 2.29 Å (φ = O, F, H〈sub〉2〈/sub〉O). The aggregate content of the 〈span〉A〈/span〉 site is (K〈sub〉1.78〈/sub〉Sr〈sub〉0.02〈/sub〉Cs〈sub〉0.01〈/sub〉Na〈sub〉0.15〈/sub〉□〈sub〉0.04〈/sub〉)〈sub〉Σ2〈/sub〉, ideally K〈sub〉2〈/sub〉〈span〉apfu〈/span〉. The 〈sup〉[10]〈/sup〉〈span〉B〈/span〉 site is occupied by (Na〈sub〉0.88〈/sub〉Ca〈sub〉0.12〈/sub〉), 〈〈span〉B〈/span〉–φ〉 = 2.646 Å. The 〈span〉W〈/span〉〈sub〉A〈/sub〉 site is occupied at 7.5% by H〈sub〉2〈/sub〉O: [□〈sub〉1.85〈/sub〉(H〈sub〉2〈/sub〉O)〈sub〉0.15〈/sub〉] 〈span〉pfu〈/span〉. The presence of OH and H〈sub〉2〈/sub〉O groups in the laverovite structure was confirmed by infrared spectroscopy. The mineral is named “laverovite” after Professor Nikolay Pavlovich Laverov (1930–2016), Academician of the Russian Academy of Sciences, a prominent Russian ore geologist and an expert in uranium ore deposits and radiogenic waste disposal. Laverovite is a Mn-analogue of zircophyllite, K〈sub〉2〈/sub〉NaFe〈sup〉2+〈/sup〉〈sub〉7〈/sub〉Zr〈sub〉2〈/sub〉(Si〈sub〉4〈/sub〉O〈sub〉12〈/sub〉)〈sub〉2〈/sub〉O〈sub〉2〈/sub〉(OH)〈sub〉4〈/sub〉F. 〈/span〉

Description: Here we report the crystal structure of zircophyllite, ideally K 2 NaFe 2+ 7 Zr 2 (Si 4 O 12 ) 2 O 2 (OH) 4 F, from Mont Saint-Hilaire, Québec, Canada. This is the first determination of the crystal structure of zircophyllite, which was originally described by Kapustin (1972) . Zircophyllite is a mineral of the astrophyllite group of the astrophyllite supergroup. Chemical analysis by electron microprobe gave SiO 2 31.89, Al 2 O 3 1.54, Na 2 O 1.91, K 2 O 6.13, Rb 2 O 0.19, Cs 2 O 0.10, CaO 0.62, SrO 0.10, MgO 0.22, ZnO 0.48, FeO 17.60, MnO 17.19, TiO 2 4.48, ZrO 2 8.65, Nb 2 O 5 2.07, F 1.36, (H 2 O) calc. 2.53, sum 96.48 wt.%; H 2 O was calculated from crystal-structure analysis. The empirical formula based on 31 (O + F) pfu is (K 1.85 Rb 0.03 Cs 0.01 Na 0.05 ) 1.94 (Na 0.83 Ca 0.16 Sr 0.01 ) 1 (Fe 2+ 3.48 Mn 3.44 Zn 0.08 Mg 0.08 ) 7.09 (Zr 1.00 Ti 0.80 Nb 0.22 ) 2.02 [(Si 7.54 Al 0.43 ) 7.97 O 24 ]O 2 [(OH) 3.98 F 0.02 ] 4 F, Z = 1, D calc. = 3.365 g/cm 3 . Zircophyllite is triclinic, space group P , a 5.447(2), b 11.966(5), c 11.789(4) Å, α 112.95(1), β 94.688(6), 103.161(7)°, V 676.4(7) Å 3 . The crystal structure has been refined from a twinned crystal to R 1 = 3.79% for 3657 unique ( F o 〉 4 F ) reflections. In the crystal structure of zircophyllite, the four [4] T sites, with 〈T–O〉 = 1.626 Å, are occupied mainly by Si, with minor Al. The [6] D site is occupied by Zr 1.00 Ti 0.78 Nb 0.20 , ideally Zr 2 apfu , with 〈D–〉 = 2.013 Å ( = O, F). The T 4 O 12 astrophyllite ribbons and D octahedra constitute the H (Heteropolyhedral) sheet. In the O (Octahedral) sheet, the four [6] M (1–4) sites, with 〈M–〉 = 2.173 Å ( = O, OH), are occupied by (Fe 2+ 3.48 Mn 3.44 Zn 0.04 Mg 0.04 ), ideally Fe 2+ 7 apfu . The central O sheet and two H sheets form the HOH block, and adjacent HOH blocks link via a common anion (X P D = F) of two D octahedra. In the I (Intermediate) block between adjacent HOH blocks, the two interstitial cation sites, [13] A and [10] B , are ideally occupied by K 2 and Na apfu , 〈A–〉 = 3.338 Å and 〈B–〉 = 2.650 Å ( = O, F). Zircophyllite is a Zr-analogue of astrophyllite, K 2 NaFe 2+ 7 Ti 2 (Si 4 O 12 ) 2 O 2 (OH) 4 F. Zircophyllite and astrophyllite are related by the substitution: D Zr 4+ D Ti 4+ .

Description: The crystal structure of jinshajiangite from the Verkhnee Espe deposit, Kazakhstan, NaBaFe 2+ 4 Ti 2 (Si 2 O 7 ) 2 O 2 (OH) 2 F, was refined from a twinned crystal to R 1 = 3.13% on the basis of 6745 unique reflections [ F o 〉 4 F o ], space group , Z = 8, a 10.7059(5), b 13.7992(7), c 20.760(1) Å, α 90.008(1), β 94.972(1), 89.984(1)°, V 3055.4(4) Å 3 . The crystal used for the structure refinement was analyzed by electron microprobe. The empirical formula was calculated on 19 (O + F), with (OH + F) = 3 pfu : (Na 0.77 Ca 0.23 ) 1 (Ba 0.60 K 0.36 ) 0.96 (Fe 2+ 2.33 Fe 3+ 0.26 Mn 1.26 Zr 0.04 Mg 0.02 Zn 0.01 ) 3.92 (Ti 1.79 Nb 0.18 Mg 0.02 Al 0.01 ) 4 (Si 2 O 7 ) 2 O 3.93 H 1.93 F 1.07 , Z = 8; Fe 2 O 3 was calculated by analogy with jinshajiangite from Norra Karr, Sweden ( Sokolova et al . 2009a ) and H 2 O from the crystal-structure analysis. In the crystal structure, TS (Titanium Silicate) and I (Intermediate) blocks alternate along c . The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). The topology of the TS block is as in Group II of the TS-block minerals where Ti (+ Nb) = 2 apfu . In the O sheet, ten [6] M O sites are occupied mainly by Fe 2+ , with 〈M O –〉 = 2.181 Å. In the H sheet, four [6] M H sites are occupied mainly by Ti, with 〈M H –〉 = 1.954 Å, and eight [4] Si sites are occupied by Si, with 〈Si–O〉 = 1.622 Å. The M H octahedra and Si 2 O 7 groups constitute the H sheet. Fluorine atoms and OH groups are ordered at the X P M (H sheet) and X O A (O sheet) sites, respectively. The TS blocks link via common vertices of M H octahedra, i.e ., M H –X P M – M H bridges. In the I block, Ba and K occur at the two A P sites, with Ba 〉 K, and the two B P sites are occupied by Na and Ca, with Na 〉 Ca. Jinshajiangite is isostructural with bobshannonite, Na 2 KBa(Nb,Ti) 4 Mn 8 (Si 2 O 7 ) 4 O 4 (OH) 4 (O,F) 2 , Z = 4.

Description: There are 40 TS-block (Titanium–Silicate) minerals, which are divided into four groups, based on the topology and stereochemistry of the TS block. Each group of structures has a different linkage, content, and stereochemistry of Ti (+ Nb + Zr + Fe 3+ + Mg + Mn). In the crystal structures of TS-block minerals, TS blocks either link directly or alternate with I (Intermediate) blocks. All TS-block structures are characterized by a planar cell based on minimal lengths of translational vectors t 1 and t 2 , t 1 ~ 5.4 and t 2 ~ 7 Å, and t 1 ^ t 2 90°. Barium is an I -block cation in 20 TS minerals. In the I block, Ba atoms form a close-packed layer. Ba occurs in Groups II–IV, but does not occur in Group I where TS-blocks link directly and an I block is absent. In TS-block structures, there are three types of I block containing Ba atoms. The type-1 I block is a layer of Ba atoms parallel to the TS block with [5]-coordinated Ti in the H sheets. The type-2 I block consists of a central layer of cation polyhedra and two adjacent layers of Ba associated with [5]- and [6]-coordinated Ti in the H sheets. For the crystal structures with I blocks of type-1 and type-2, the lengths of the t 1 and t 2 vectors are t 1 ~ 5.4 and t 2 ~ 7 Å. The type-3 I block consists of a layer of Ba or Ba (+ K + Na) atoms associated with [6]-coordinated Ti in the H sheets. The F and O atoms that are apical anions of [6]-coordinated Ti occur in the layer of Ba atoms. The crystal structure is based on two translation vectors, t 1 and t 2 ; the lengths of these vectors are doubled: 2 t 1 ~ 10.8 and 2 t 2 ~ 14 Å. In structures with the type-3 I block, doubled minimal translations are due to distortion of rings of polyhedra in the H sheets. This distortion of rings of polyhedra is necessary to satisfy bond-valence requirements on X P M anions, where X P M = F, O. In the type-3 I block, the X P M site is coordinated by four or six cations and there is no space to accommodate an OH group plus a hydrogen bond at that site. Hydroxyl groups occur at the X O A sites in the O sheet where each X O A anion is bonded to three M O cations. Hence F atoms are ordered at the X P M sites on the periphery of the TS block and OH groups are ordered at the X O A sites in the O sheet.

Description: The crystal structure and chemical formula of bafertisite, Ba 2 Fe 2+ 4 Ti 2 (Si 2 O 7 ) 2 O 2 (OH) 2 F 2 , have been revised. Three samples of bafertisite were studied using electron-microprobe analysis, Mössbauer spectroscopy, IR and Raman spectroscopy, and single-crystal X-ray diffraction. These samples are from (1) the Bayan Obo REE deposit, Inner Mongolia, China (holotype); (2) the Gremyakha-Vyrmes alkaline complex, Kola Peninsula, Russia; and (3) the Darai-Pioz alkaline massif, Tajikistan. Bafertisite is a TS-block mineral of Group II, Ti = 2 apfu (atoms per formula unit) per (Si 2 O 7 ) 2 ( Sokolova 2006 ). Bafertisite is triclinic, C , a 10.677(6), b 13.767(7), c 11.737(5) Å, α 90.12(1), β 112.28(4), 90.02(1)°, V 1596(3) Å 3 (unit-cell parameters are for bafertisite from Kola, sample 2). Chemical analysis was done by electron microprobe, the H 2 O content was calculated from the crystal-structure solution and refinement, and the occurrence of Fe 2+ and lack of Fe 3+ were confirmed by Mössbauer spectroscopy. The empirical formulae were calculated on the basis of 20 (O + F) anions, with (OH + F) = 4 apfu, and they are of the form A P 2 M O 4 M H 2 (Si 2 O 7 ) 2 (X O ) 4 (X P ) 2 , Z = 4: (1) (Ba 1.89 K 0.03 ) 1.92 (Fe 2+ 3.33 Mn 0.47 Mg 0.11 ) 3.91 (Ti 1.86 Nb 0.07 Zr 0.02 Mg 0.05 ) 2 (Si 2.05 O 7 ) 2 O 2 [(OH) 1.82 F 0.18 ] 2 F 2 ; (2) (Ba 1.82 Sr 0.02 K 0.02 ) 1.86 (Fe 2+ 3.24 Mn 0.57 Al 0.06 Mg 0.03 Ca 0.01 Zr 0.01 Zn 0.01 Na 0.02 ) 3.95 (Ti 1.96 Nb 0.03 Zr 0.01 ) 2 (Si 2.05 O 7 ) 2 O 2 [(OH) 1.59 F 0.41 ] 2 F 2 ; and (3) (Ba 1.90 K 0.02 ) 1.92 (Fe 2+ 2.23 Mn 1.61 Mg 0.02 Zr 0.04 Zn 0.03 ) 3.93 (Ti 1.90 Nb 0.09 Zr 0.01 ) 2 (Si 2.03 O 7 ) 2 O 2 [(OH) 1.75 F 0.25 ] 2 F 2 . The crystal structures of (1), (2), and (3) were solved and refined from twinned crystals to R 1 = 2.90, 2.46, and 2.74% on the basis of 4538, 4685, and 4692 unique reflections (| F | 〉 4| F |) and can be described as a combination of a TS (Titanium Silicate) block and an I (Intermediate) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). The topology of the TS block is as in Group II of the Ti disilicates: Ti + Nb = 2 apfu per (Si 2 O 7 ) 2 (as defined by Sokolova 2006 ). Here we report structure-refinement results for bafertisite from Kola, sample (2), with the lowest value of R 1 = 2.46%. In the O sheet, five [6] M O sites are occupied mainly by Fe 2+ , less Mn, and minor Mg, Al, Zr, Zn, and Ca, with 〈M O –〉 = 2.179 Å ( = O,OH), and they ideally give Fe 2+ 4 apfu . In the H sheet, two [6] M H sites are occupied mainly by Ti, with 〈M H –〉 = 1.963 Å ( = O,F), and they ideally give Ti 2 apfu ; four [4] Si sites are occupied by Si, with 〈Si–O〉 = 1.626 Å. The M H octahedra and Si 2 O 7 groups constitute the H sheet. The two [12] Ba-dominant A P (1,2) sites, with 〈A P –〉 = 2.979 Å ( = O, F), ideally give Ba 2 apfu . Two X O M (1,2) and two X O A (1,2) sites are occupied by O atoms and OH groups with minor F, respectively, ideally giving (X O ) 4 = (X O M ) 2 + (X O A ) 2 = O 2 (OH) 2 pfu . Two X P M (1,2) sites are occupied by F, giving F 2 apfu . TS blocks link via a layer of Ba atoms which constitute the I block. Simplified and endmember formulae of bafertisite are Ba 2 (Fe 2+ ,Mn) 4 Ti 2 (Si 2 O 7 ) 2 O 2 (OH,F) 2 F 2 and Ba 2 Fe 2+ 4 Ti 2 (Si 2 O 7 ) 2 O 2 (OH) 2 F 2 , Z = 4.

Description: Bulgakite, ideally Li 2 (Ca,Na)Fe 2+ 7 Ti 2 (Si 4 O 12 ) 2 O 2 (OH) 4 (O,F)(H 2 O) 2 , and nalivkinite, ideally Li 2 NaFe 2+ 7 Ti 2 (Si 4 O 12 ) 2 O 2 (OH) 4 F(H 2 O) 2 , are astrophyllite-supergroup minerals. Bulgakite is a new mineral from the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river, in the area of the joint Turkestansky, Zeravshansky, and Alaisky ridges, Tajikistan. Bulgakite was found in fenitized amphibole–quartz–feldspar rock with brannockite, sogdianite, bafertisite, albite, and titanite. Bulgakite is brownish orange, transparent in thin grains, and has a vitreous luster. Mohs hardness is 3, D meas. = 3.30(2) g/cm 3 , D calc. = 3.326 g/cm 3 . Bulgakite is biaxial (+) with refractive indices ( = 589 nm) α = 1.695(3), β = 1.711(2), = 1.750(3); 2 V meas. = 70(5)°, 2 V calc. = 67°, strong dispersion: r 〉 v . Cleavage is perfect parallel to {001} and moderate parallel to {010}. Chemical analysis by electron microprobe gave SiO 2 35.63, Al 2 O 3 0.95, Na 2 O 1.04, K 2 O 3.27, Cs 2 O 0.31, CaO 2.56, MgO 0.16, ZnO 0.15, FeO 29.24, MnO 7.14, TiO 2 11.07, Nb 2 O 5 0.49, ZrO 2 0.37, SnO 2 1.18, F 1.01, Li 2 O 1.36 (AAS), Rb 2 O 0.85 (AAS), (H 2 O) calc. 4.04, sum 100.38 wt.%, H 2 O was calculated from crystal-structure analysis. The empirical formula based on 31.94 (O + OH + F + H 2 O) pfu is (Li 0.94 K 0.91 Rb 0.12 Cs 0.03 ) 2 (Ca 0.60 Na 0.40 ) 1 (Fe 2+ 5.34 Mn 1.32 Li 0.25 Mg 0.05 Na 0.04 Zn 0.02 ) 7.02 (Ti 1.82 Sn 0.10 Nb 0.05 Zr 0.04 ) 2.01 [(Si 7.78 Al 0.24 ) 8.02 O 24 ]O 2 (OH) 4 (F 0.70 O 0.30 )[(H 2 O) 0.94 1.06 ] 2 , Z = 1. Bulgakite is triclinic, space group P , a 5.374(1), b 11.965(2), c 11.65(3) Å, α 113.457(8), β 94.533(8), 103.08(1)°, V 657.5(8) Å 3 . The six strongest reflections in the X-ray powder diffraction data [ d (Å), I, ( hkl )] are: 10.54, 100, (001); 3.50, 100, (003); 2.578, 100, (130); 2.783, 90, (1 2); 1.576, 68, (3 1, 2); 2.647, 55, ( 11). The crystal structure has been refined to R 1 = 2.6% for 3592 unique F o 〉 4 F ) reflections. In the crystal structure of bulgakite, there are four [4] T sites, with 〈 T –O〉 = 1.626 Å, occupied mainly by Si, with minor Al. The TO 4 tetrahedra constitute the T 4 O 12 astrophyllite ribbon. The [6] D site is occupied mainly by Ti, with 〈 D –〉 = 1.965 Å ( = O, F). The T 4 O 12 astrophyllite ribbons and D octahedra constitute the H (Heteropolyhedral) sheet. In the O (Octahedral) sheet, there are four Fe 2+ -dominant [6] M (1–4) sites, with 〈M–〉 = 2.159 Å ( = O, OH). Two H and the central O sheets form the HOH block, and adjacent HOH blocks link via a common anion (X P D ) of two D octahedra. In the I (Intermediate) block between adjacent HOH blocks, there are two interstitial cation sites, A and B , and a W site, partly occupied by H 2 O. The A site splits into two partly occupied sites, [13] A (1) and [6] A (2), with A(1)–A(2) = 1.16 Å. The [6] A (2) site is occupied by Li with 〈A(2)–〉 = 2.285 Å ( = O, F, H 2 O), and the [13] A (1) site is occupied by K, Rb, and Cs with 〈A(1)–〉 = 3.298 Å. The aggregate content of the A site is (Li 0.94 K 0.91 Rb 0.12 Cs 0.03 ) 2 , ideally Li 2 apfu . The [10] B site is occupied by (Ca 0.60 Na 0.40 ) with 〈 B –〉 = 2.593 Å. The W site is occupied by [(H 2 O) 0.94 1.06 ] 2 pfu . The mineral is named bulgakite after Lev Vasil'evich Bulgak (born 1955), Russian mineralogist, gemologist, and discoverer of several new minerals. The crystal structure of nalivkinite has been revised and refined to R 1 = 4.52% for 3546 unique ( F o 〉 4 F ) reflections: space group P , a 5.374(3), b 11.948(5), c 11.676(5) Å, α 113.360(6), β 94.538(8), 103.01(1)°, V 658.7(9) Å 3 , Z = 1, D calc. = 3.347 g/cm 3 . The revised empirical formula of nalivkinite is based on 32.14 (O + OH + F + H 2 O) pfu : (Li 1.14 K 0.75 Cs 0.09 Pb 0.02 ) 2 (Na 0.71 Ca 0.29 ) 1 (Fe 2+ 5.62 Mn 0.90 Zr 0.08 Na 0.08 Mg 0.04 Zn 0.04 ) 6.76 (Ti 1.56 Nb 0.24 Sn 0.09 Zr 0.08 Ta 0.04 ) 2 [(Si 7.86 Al 0.15 ) 8.01 O 24 ]O 2 (OH) 4 F[(H 2 O) 1.14 0.86 ] 2 . The presence of H 2 O groups in the bulgakite and nalivkinite structures was confirmed by infrared spectroscopy. Bulgakite is a Ca-analogue of nalivkinite. Bulgakite and nalivkinite are related by the following substitution: 0.3 B Ca 2+ + 0.3 X O 2– 0.3 B Na + + 0.3 X F – .