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Tsepinite- Ca, ideally (Ca,K,Na, h )2(Ti,Nb)2(Si4O12)(OH,O)2·4H2O (Z = 4), is a new mineral species of the labuntsovite group (vuoriyarvite subgroup) found in the abandoned Lovchorrite mine, Hackman Valley, Yukspor Mountain, Khibiny massif, Kola Peninsula, Russia. It occurs in the hydrothermally altered zone of a large aegirine- nepheline- potassic feldspar pegmatite and is associated mainly with microcline, aegirine, natrolite, kentbrooksite, kupletskite, Mn-rich lamprophyllite, fluorapatite, catapleiite, ancylite- (Ce), ancylite- (La), fluorapo- phyllite, leucophanite, chabazite- Ca. The new mineral is late hydrothermal and oc- curs in cavities after leaching of rinkite, the probable source of Ti, Nb and Ca. Tse- pinite- Ca forms coarse long-prismatic to needle-shaped and usually split crystals which are transparent, colourless to white and pale brownish, up to 0.2 ´0.6´5mm in size and form aggregates up to 1cm in size. The streak is white and the lustre is vitreous. Tsepinite- Ca is brittle, shows uneven fracture and no cleavage. Its Mohs' hardness is 5; Dmeas. = 2.73(1), Dcalc. = 2.72g/cm 3 . Biaxial (+), 2Vmeas. = 30 ± 10ƒ, 2Vcalc. = 36ƒ; a = 1.666(2), b = 1.676(2), g = 1.780(4). Dispersion is very weak: r < n. Non-pleochroic; the orientation is Y = b. The strongest IR bands (cm -1 ) are at 3260, 1103, 946, 673, 455. Electron microprobe analysis (H 2O by TGA) gave: Na 2O

Bornemanite is a rare alkali titanosilicate occurring in the natrolite zone of the Yubileynaya hyperagpaitic pegmatite, on Karnasurt Mountain, in the Lovozero massif, Kola Peninsula, Russia. The mineral is light yellow, lamellar (001) and elongate [010]. No single crystals suitable for X-ray crystallography are available. New electron-microprobe chemical analyses, selected area electron diffraction (SAED) and X-ray powder diffraction show that bornemanite, BaNa 3{(Na,Ti)4[(Ti,Nb)2O2Si4O14] (F,OH)2}PO4, is monoclinic I11b, a 5.498(4), b 7.120(6), c 47.95(4) A, � 88.4(1)°; Z = 4. By comparison with structural and chemical data for titanosilicates based on a bafertisite-like layer (heterophyllosilicates), a model of the structure of bornem anite has been obtained. This model has been refined by the distance least-squares technique (DLS program) and tested against calculated powder-diffraction and SAED patterns. The structure of bornemanite can be described as a [001] stacking of heterophyllosilicate layers, where lomonosovite and seidozerite contents alternate in the interlayer spaces. Thus this structur e is the first documented case of a heterophyllosilicate based on modules of two other structures belonging to the same modular series, i.e., the mero-plesiotype bafertisite series. The lomonosovite–seidozerite polysomatic series is defined. In contrast to the original description, bornemanite is considered monoclinic and not orthorhombic, and lacks one cation per formula unit (mainly Na). Possible leaching of alkalis and the solid-state oriented transformation lomonosovite → bornemanite are discussed.

Several structural families reported in this book can be described by using concepts of modular crystallography (Thompson 1978; Veblen 1991; Merlino 1997; Ferraris et al. 2004). This chapter presents three groups of microporous minerals emphasizing the modular aspects of their crystal structures and the role that modularity plays in correlating different structures as well as structure and properties, namely aspects aimed at an engineering of microporous materials (cf. Rocha and Lin 2005). The description of a crystal structure as an edifice consisting of complex building modules that occur also in other structures implicitly leads to identify features that are common to a group of compounds. This kind of group can often be expressed as a series of structures that are collinear in composition and cell parameters, information that may be crucial to model unknown structures related to the series, as illustrated by some examples in this chapter. Biopyriboles (Fig. 1⇓) represent a first and now classical example of modular structures established by Thompson (1978). He showed that the structures of micas, pyroxenes and amphiboles share, according to different ratios, the same modules of mica ( M ) and pyroxene ( P ) and are members of a polysomatic series MmPp . The ideal chemical composition and cell parameters of the members of the series are linear functions of the ratio m / p . The classification of biopyriboles as members of a polysomatic series, a type of series belonging to the wider category of the homologous series (cf. Ferraris et al. 2004), and the consequent discovery of the multiple-chain-width biopyriboles jimthompsonite and chesterite (Veblen and Buseck 1979) dramatically proved the predictive power of these series in terms of structure characterization and modeling. The modeling of carlosturanite (Mellini et al. 1985) and of other modular structures …

Kristiansenite occurs as a late hydrothermal mineral in vugs in an amazonite pegmatite at Heftetjern, Tordal, Telemark, Norway. Tapering crystals, rarely up to 2 mm long, are colourless, white, or slightly yellowish. The mineral has the ideal composition Ca2ScSn(Si2O7)(Si2O6OH) and is triclinic C1 with cell parameters a = 10.028(1), b = 8.408(1), c = 13.339(2) A, α = 90.01(1), β = 109.10(1), γ = 90.00(1)°, V = 1062.7(3) A3 (Z = 4). It has a monoclinic cell within ∼ 0.1 A and is polysynthetically twinned on {010} by metric merohedry. The strongest reflections in the X-ray powder pattern are [d in A, (I obs), (hkl)]: 5.18 (53) (1–11), 3.146 (100) (004), 3.089 (63) (−222), 2.901 (19) (221), 2.595 (34) (222), 2.142 (17) (−3–31). The Mohs’ hardness is 5½–6; Dcalc. = 3.64 g/cm3; only a mean refractive index of 1.74 could be measured. Scandium enrichment in the Heftetjern pegmatite and the crystal chemistry of scandium are briefly discussed.

The structure refinement of associated phlogopite-2 O and phlogopite-1 M from the Khibiny massif (Kola Peninsula, Russia) is reported. Crystal data are: α = 5.2781(5), b = 9.141(1), c = 20.124(4) A, Ccmm (20); a = 5.305(2), b = 9.199(2), c = 10.232(4) A, β = 100.03(2)°, C 2/m (1 M ). Least-squares refinement of single-crystal X-ray diffraction data converged to R1 = 0.034 (2 O , 926 independent reflections) and 0.037 (1 M , 677 independent reflections). This is the first structure refinement of an MDO (standard) mica-2 O : two previous structure reports concerned anandite-2 O , which was not a true polytype, having an oP (primitive orthorhombic) lattice not compatible with the C -centred cell common to all mica polytypes. The two phlogopite polytypes show practically the same chemical composition (K 0 . 95Na 0.01 ) (Mg 2.16 Fe 0.34 Ti 0.04 Mn 0.04 Li 0.40 )[Si 3.40 Al 0.60 O 10 ][(OH) 1.35 F 0 .65] and no cation ordering. Both polytypes are affected by stacking disorder, which broadens the non-family reflections ( k ≠ 3n). As a consequence, the diffracted intensities of the two types are measured at different scales and large residues in the difference Fourier maps were observed at ± b /3 along [010], [310] and [310]. These residues ( uroviceffect ) disappear by carrying out the refinement with separate scale factors for the two types of reflections. On the basis of structural, morphology and zoning considerations the formation of the two associated polytypes is attributed to chemical oscillation in the crystallization mean.