Patynite, NaKCa4[Si9O23], a New Mineral from the Patynskiy Massif, Southern Siberia, Russia

The new mineral patynite was discovered at the massif of Patyn Mt. (Patynskiy massif), Tashtagolskiy District, Kemerovo (Kemerovskaya) Oblast’, Southern Siberia, Russia. Patynite forms lamellae up to 1 0.5 cm and is closely intergrown with charoite, tokkoite, diopside, and graphite. Other associated minerals include monticellite, wollastonite, pectolite, calcite, and orthoclase. Patynite is colorless in individual lamellae to white and white-brownish in aggregates. It has vitreous to silky luster, white streaks, brittle tenacity, and stepped fractures. Its density measured by flotation in Clerici solution is 2.70(2) g/cm3; density calculated from the empirical formula is 2.793 g/cm3. The Mohs’ hardness is 6. Optically, patynite is biaxial (–) with α = 1.568(2), β = 1.580(2), and γ = 1.582(2) (589 nm). The 2V (measured) = 40(10) and 2V (calculated) = 44.1. The Raman and IR spectra shows the absence in the mineral of H2O, OH–, and CO32– groups and B–O bonds. The chemical composition is (electron microprobe, wt.%): Na2O 3.68, K2O 5.62, CaO 26.82, SiO2 64.27, total 100.39. The empirical formula based on 23 O apfu is Na1.00K1.00Ca4.02Si8.99O23. Patynite is triclinic, space group P–1. The unit-cell parameters are: a = 7.27430(10), b = 10.5516(2), c = 13.9851(3) Å, α = 104.203(2)°, β = 104.302(2)°, γ = 92.0280(10)°, V = 1003.07(3) Å3, Z = 2. The crystal structure was solved by direct methods and refined to R1 = 0.032. Patynite is an inosilicate with a new type of sextuple branched tubular chain [(Si9O23)10–] with an internal channel and [(Si18O46)20–] as the repeat unit. The strongest lines of the powder X-ray diffraction pattern [dobs, Å (I, %) (hkl)] are: 3.454 (100) (2-1-1), 3.262 (66) (2-1-2), 3.103 (64) (02-4), 2.801 (21), 1.820 (28) (40-2). Type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia with the registration number 5369/1.


Introduction
Inosilicates represent a very large group of minerals with chain structures. Amongst them, only five mineral species, namely, calcinaksite KNaCa(Si 4 O 10 )·H 2 O [1], canasite K 3 Na 3 Ca 5 Si 12 O 30 (OH) 4 [2,3], fluorcanasite K 3 Na 3 Ca 5 Si 12 O 30 F 4 ·H 2 O [4], its dimorph frankamenite Geologically, Patynskiy massif belongs to an Early Devonian gabbro-syenite formation. It occupies an approximate area of 50 km 2 and has an isometric outline. Its contacts fall from the periphery to the central part showing a funnel form of the massif. Patynskiy massif was formed in near-surface conditions and, most probably, represents a subvolcano. It is composed mainly of basic rocks including different types of gabbro (olivine and titanomagnetite ones with coarse grained pegmatoid, vesicular, and porphyritic textures), as well as troctolites, norites, pyroxenites, anorthosites, etc. Other types of rocks are represented by rare dikes of microgranites, selvsbergites, grorudites, veins of monticellite-melilite-nepheline rocks, acid and alkaline pegmatites, and alkaline Geologically, Patynskiy massif belongs to an Early Devonian gabbro-syenite formation. It occupies an approximate area of 50 km 2 and has an isometric outline. Its contacts fall from the periphery to the central part showing a funnel form of the massif. Patynskiy massif was formed in near-surface conditions and, most probably, represents a subvolcano. It is composed mainly of basic rocks including different types of gabbro (olivine and titanomagnetite ones with coarse grained pegmatoid, vesicular, and porphyritic textures), as well as troctolites, norites, pyroxenites, anorthosites, etc. Other types of rocks are represented by rare dikes of microgranites, selvsbergites, grorudites, veins of monticellite-melilite-nepheline rocks, acid and alkaline pegmatites, and alkaline syenites. While basic Minerals 2019, 9, 611 3 of 19 rocks are strongly dominant throughout the massif and show a concentric-zonal structure, other ones are spread out locally in central and south-western parts of the massif. All these rocks are studied in detail and described in the geologic literature [10][11][12][13].
The north-eastern part of Patynskiy massif has been rarely studied; it was considered by geologists as unpromising for industrial mineralization. In this area, the collecting group discovered an outcrop of diopside-wollastonite skarns, 15 m in width, confined to the contact of pyroxenite with marmorized limestone. The samples containing patynite were collected approximately 200 m from the outcrop, in the alluvium of the small river Pravyi (Right) Sunzas (a left tributary of the Bazas river), 2 km below its head ( Figure 2).
Minerals 2017, 7, x FOR PEER REVIEW 3 of 18 syenites. While basic rocks are strongly dominant throughout the massif and show a concentric-zonal structure, other ones are spread out locally in central and south-western parts of the massif. All these rocks are studied in detail and described in the geologic literature [10][11][12][13].
The north-eastern part of Patynskiy massif has been rarely studied; it was considered by geologists as unpromising for industrial mineralization. In this area, the collecting group discovered an outcrop of diopside-wollastonite skarns, 15 m in width, confined to the contact of pyroxenite with marmorized limestone. The samples containing patynite were collected approximately 200 m from the outcrop, in the alluvium of the small river Pravyi (Right) Sunzas (a left tributary of the Bazas river), 2 km below its head ( Figure 2). The new mineral was discovered in a single large boulder measuring 70 × 50 × 40 cm in size and weighing 50 kg ( Figure 3). Its main part consists of white to light blue fine-grained diopside closely intergrown with snow-white monticellite and pale-blue wollastonite-2M. Patynite occurs in the middle part of the boulder as lamellar aggregates with a characteristic stepped fracture, intimately intergrown with charoite, tokkoite, white and green diopside, and graphite. Other minerals found in the boulder were pectolite, calcite, and orthoclase. This assemblage and the place of patynite discovery indicate that this mineral has a metasomatic origin and most likely comes from the abovementioned skarns. The new mineral was discovered in a single large boulder measuring 70 × 50 × 40 cm in size and weighing 50 kg ( Figure 3). Its main part consists of white to light blue fine-grained diopside closely intergrown with snow-white monticellite and pale-blue wollastonite-2M. Patynite occurs in the middle part of the boulder as lamellar aggregates with a characteristic stepped fracture, intimately intergrown with charoite, tokkoite, white and green diopside, and graphite. Other minerals found in the boulder were pectolite, calcite, and orthoclase. This assemblage and the place of patynite discovery indicate that this mineral has a metasomatic origin and most likely comes from the above-mentioned skarns.
The mineral association of patynite with charoite and tokkoite is noteworthy. The two latter minerals were discovered in charoitites of the Murun alkaline massif in Eastern Siberia [8,9,[14][15][16][17], and until the present time, were considered as endemics. Our find is, therefore, the second in the world for both of these minerals.
Similar to the charoite from Murun, this one from the Patynskiy massif forms long-fibrous aggregates with vitreous to silky luster and has good cleavage in three directions. The main difference between the charoite varieties from the two localities is the color. Charoite from its type locality is famous for purple to violet coloration caused by traces of Mn 3+ , whereas charoite from the Patynskiy massif is whitish-grey to brown. Its chemical composition is as follows (wt.%, average of five analyses, H 2 O calculated from the deficiency of the analysis total): Na 2   The mineral association of patynite with charoite and tokkoite is noteworthy. The two latter minerals were discovered in charoitites of the Murun alkaline massif in Eastern Siberia [8,9,[14][15][16][17], and until the present time, were considered as endemics. Our find is, therefore, the second in the world for both of these minerals.
Similar to the charoite from Murun, this one from the Patynskiy massif forms long-fibrous aggregates with vitreous to silky luster and has good cleavage in three directions. The main difference between the charoite varieties from the two localities is the color. Charoite from its type locality is famous for purple to violet coloration caused by traces of Mn 3+ , whereas charoite from the Patynskiy massif is whitish-grey to brown. Its chemical composition is as follows (wt.%, average of five analyses, H2O calculated from the deficiency of the analysis total): Na2O 1.87; K2O [15], differing from the latter by the total absence of admixed Sr and F and a substantially higher Ca content. The monoclinic unit-cell dimensions calculated from the powder X-ray diffraction pattern of charoite from the Patynskiy massif are: a = 31.859  [16].

Methods
The Raman spectrum of patynite was obtained from a polished section by means of a Horiba Labram HR Evolution spectrometer (Jobin Yvon, Palaiseau, France. This dispersive, edge-filter-based system is equipped with an Olympus BX 41 optical microscope (Olympus Company, Shinjuku, Japan), a diffraction grating with 600 grooves per millimeter, and a Peltier-cooled, Si-based charge-coupled device (CCD) detector. After careful tests with different lasers (473, 532, and 633 nm), the 633 nm He-Ne laser with the beam power of 10 mW at the sample surface was selected for spectra acquisition to minimize analytical artefacts. Raman signal was collected in the range of 100-4000 cm −1 with a 100x objective (NA 0.9) and the system operated in the confocal mode, beam diameter was~1 µm, and the lateral resolution~2 µm. No visual damage of the analyzed surface was observed at these conditions after the excitation. Wavenumber calibration was done using the Rayleigh line and low-pressure Ne-discharge lamp emissions. The wavenumber accuracy was~0.5 cm −1 , and the spectral resolution was~2 cm −1 . Band fitting was done after appropriate background correction, assuming combined Lorentzian-Gaussian band shapes using the Voight function (PeakFit; Version number 4.12, originally developed by Jandel Scientific, Erkraht, Germany, now distributed by Systat software Inc., San Jose, CA, USA).
In order to obtain the IR absorption spectrum of patynite, hand-picked fragments were ground in an agate mortar, mixed with anhydrous KBr, pelletized, and analyzed using an ALPHA FTIR spectrometer (Bruker Optics, Ettlingen, Germany) in the range of wavenumbers from 360 to 3800 cm −1 , with a spectral resolution of 4 cm −1 . The IR spectrum of a pure KBr disk was used as a reference.
Chemical analyses (11 points) were carried out with a Cameca SX-100 electron microprobe (Cameca company, part of Ametek group, Gennevilliers Cedex, France) (WDS mode, 15 kV, 10 nA, 8 µm beam diameter). The following standards were used: albite for Na, orthoclase for K, andradite for Ca, and sanidine for Si. No other elements were found above the detection limit. Raw intensities were processed by the X-PHI matrix correction algorithm.
The single-crystal X-ray diffraction experiment was carried out on a grain of patynite with the size 0.10 × 0.06 × 0.02 mm 3 . It was extracted from the polished section, analyzed using electron microprobe, then mounted on a glass fiber and examined with a Supernova Rigaku-Oxford Diffraction diffractometer (Rigaku-Oxford Diffraction, Neu Isenbrug, Germany) equipped with a Pilatus 200 K Dectris detector (Dectris, Baden-Daettwil, Switzerland) and a X-ray micro-source (MoKα radiation) with spot of 0.12 mm. The detector-to-sample distance was 68 mm. A full sphere of three-dimensional data was collected. Data reduction was performed using CrysAlisPro (Rigaku-Oxford Diffraction, Neu Isenbrug, Germany). The data were corrected for Lorentz factor and polarization effect, and the absorption correction was performed by running the interframe scaling implemented in CrysAlisPro (ver. 1.171.40.55a, Neu Isenbrug, Germany).
Powder X-ray diffraction data were collected using the same X-ray instrument, which can act as a micro-powder diffractometer. A standard phi scan mode (0-360 • rotation) as implemented in the powder power tool of CrysAlis Pro ver. 1.171.40.55a was used for the powder data collection.

General Appearance, Physical, Chemical, and Optical Properties
Patynite forms lamellar aggregates up to 1 × 0.5 cm and is closely intergrown with charoite, tokkoite, diopside, and graphite (Figures 4-6). The new mineral is transparent, colorless in individual lamellae to white and white-brownish in aggregates. It has vitreous to silky luster and white streaks. The mineral is brittle, with a stepped fracture. Patynite shows two directions of perfect cleavage parallel to the individuals' elongation and one imperfect cleavage with 96 • to the individuals' elongation. Parting was not observed. The new mineral itself is not fluorescent, however, macro specimens containing patynite show bright green fluorescence under SW UV radiation, presumably due to absorbed, very thin films of unidentified, amorphous uranyl-bearing Al-Si minerals filling the microcracks at the contacts of patynite with the associated minerals. Its density measured by flotation in Clerici solution is 2.70(2) g/cm 3 ; density calculated from the empirical formula is 2.793 g/cm 3 . The Mohs' hardness based on scratching tests is 6. The mineral does not react with cold hydrochloric and nitric acids. biaxial (-) with α = 1.568(2), β = 1.580(2), γ = 1.582(2) (589 nm). The 2V estimated based on the curve of the conoscopical figure for the section perpendicular to the optical axis is 40(10), 2V (calculated) = 44.1. Dispersion of optical axes is weak, r < v. Optical Y axis is nearly parallel to the individuals' elongation.
The Gladstone-Dale compatibility index (1 -Kp/Kc) is 0.003, using the empirical formula and the unit-cell parameters determined from single-crystal X-ray data, which is rated as "superior" [18].

Raman Spectroscopy
The Raman spectrum of patynite ( Figure 7) shows the absence of absorption bands of H2O molecules, OH groups, and CO3 2-anions. The bands in the range of 1000-1200 cm -1 correspond to stretching vibrations of the Si-O-Si fragments, and the bands in the range of 900-1000 cm -1 are due to stretching vibrations of apical Si-O bonds. The bands in the 720-820 cm -1 range can be assigned to complex vibrations of tetrahedral rings ("ring bands" [19]), while those in the 600-700 cm -1 range can be assigned to O-Si-O bending vibrations. The bands below 600 cm -1 correspond to lattice modes In transmitted plain polarized light, patynite is colorless and non-pleochroic. It is optically biaxial (−) with α = 1.568(2), β = 1.580(2), γ = 1.582(2) (589 nm). The 2V estimated based on the curve of the conoscopical figure for the section perpendicular to the optical axis is 40(10) • , 2V (calculated) = 44.1 • . Dispersion of optical axes is weak, r < v. Optical Y axis is nearly parallel to the individuals' elongation.
The Gladstone-Dale compatibility index (1 − K p /K c ) is 0.003, using the empirical formula and the unit-cell parameters determined from single-crystal X-ray data, which is rated as "superior" [18].

Raman Spectroscopy
The Raman spectrum of patynite ( Assignment of the weak band at 1326 cm −1 is ambiguous. This band could correspond to trace amounts of B-O bonds, but IR spectroscopic data exclude this possibility. Therefore, we assign this band to a combination mode.

Infrared Spectroscopy
The IR spectrum of patynite (Figure 8 There is a simple correlation between the weighted average frequency νSi-O of the (Si,Al)-Ostretching vibrations (in the range from 820 to 1200 cm −1 ) and the mean number of vertices that a (Si,Al)O4 tetrahedron shares with other tetrahedra [20]. In particular, for aluminosilicates with the stoichiometry of the tetrahedral part SixAlyOz, the correlation is as follows: Consequently, for silicates that do not contain aluminum in the tetrahedral part, the following correlation is valid: t = (1827 − νSi-O)(0.6428νSi-O − 337.8) −1 , where t is the atomic O:Si ratio in the tetrahedral part of the crystal structure. For patynite, νSi-O ≈ 1020 cm −1 , which corresponds to t = 2.54. This value is close to the t value of 2.556 calculated from the idealized formula.

Infrared Spectroscopy
The IR spectrum of patynite (Figure 8) is unique and can be used as a reliable diagnostic tool. The assignment of IR absorption bands (ranges) are as follows:

Chemical Composition
Chemical data for patynite are given in Table 1. Contents of other elements with atomic numbers >8 are below detection limits.  There is a simple correlation between the weighted average frequency ν Si-O of the (Si,Al)-O-stretching vibrations (in the range from 820 to 1200 cm −1 ) and the mean number of vertices that a (Si,Al)O 4 tetrahedron shares with other tetrahedra [20]. In particular, for aluminosilicates with the stoichiometry of the tetrahedral part Si x Al y O z , the correlation is as follows: Consequently, for silicates that do not contain aluminum in the tetrahedral part, the following correlation is valid: where t is the atomic O:Si ratio in the tetrahedral part of the crystal structure. For patynite, ν Si-O ≈ 1020 cm −1 , which corresponds to t = 2.54. This value is close to the t value of 2.556 calculated from the idealized formula.

Chemical Composition
Chemical data for patynite are given in Table 1. Contents of other elements with atomic numbers >8 are below detection limits.

X-ray Diffraction Data
The crystal structure of patynite was solved by direct methods based on single-crystal X-ray diffraction data and refined using the SHELX-97 software within the WINGX package [21,22] to R 1 = 0.032 for 10,758 unique reflections with I > 2σ(I). All atoms were refined anisotropically. Patynite is triclinic, space group P1. The refined unit-cell parameters are: a = 7.27430 (10) The crystal data and the experimental details are presented in Table 2, atom coordinates, thermal displacement parameters in Tables 3 and 4, and selected interatomic distances in Table 5. In order to show the lack of evidence of oxygen-hydrogen bonds, the Bond valence calculations are given in Table 6.

Description of Crystal Structure and Discussion
Patynite is an inosilicate with tubular columns having an internal channel. Its unique structure can be described as being constituted by two types of modules: (1) One triple chain of tetrahedrally coordinated Si atoms; the chain extends along the direction of the a lattice parameter and is built up by three symmetrically independent wollastonite chains with three tetrahedra in the repeat unit; the triple chain encloses eight-membered and five-membered rings of tetrahedra ( Figure 9). The neighboring triple chains (i.e., bands) are not isolated and are related by a center of symmetry and connected in such a way that every third tetrahedron in two of the wollastonite-type chains has a common vertex with a tetrahedron of the centrosymmetric band. Thus, the six wollastonite-type chains build up a complex motif of tetrahedra corresponding to a complex column (a silicate tube) running along the a-axis (Figure 13). The stoichiometry of the silicate radical is Si 9 O 23 , and (Si 18 O 46 ) 20− is the repeat unit. Each column contains a central channel decorated with lateral strips of eight-membered distorted rings. The channel has lateral windows built of eight-membered rings and five-membered rings adjacent along the a-axis, and with saddle-distorted six-membering rings perpendicular to the a-axis (Figure 14). This kind of channel is unknown neither in other minerals with tubular silicate radicals nor in zeolites. Potassium atoms occur in the centers of the lateral eight-membered windows of the chain (Figure 14). Na atoms occupy a position within the eight-fold rings of the lateral strips attached to the columns.
form eight-and four-membered rings ( Figure 13). The corrugated layers of Ca-octahedra in tokkoite and tinaksite is also topologically different ( Figure 14).
Based on the structural data described above, patynite can be considered as a prototype of a material with heteropolyhedral structure that is capable of the selective accumulation and immobilization of large cations in structural channels.          Funding: A part of this work (infrared spectroscopy and, partly, crystal-chemicalanalysis) was financially supported by the Russian Foundation for BasicResearch, grant no. 18-29-12007-mk.     (2) Ca-centered octahedra sharing common edges form a two-fold strip running along the a lattice parameter. Adjacent strips link along the b lattice parameter by sharing common apexes to form a corrugated octahedral layer extending on the (001) plane ( Figure 10).
The other minerals whose crystal structures contain tubular silicate radicals are charoite, agrellite, and miserite [26], as well as members of the litidionite group, which includes litidionite, fenaksite, manaksite, and calcinaksite [27]. All these minerals differ significantly from patynite in the structures of the silicate tubes, chemical composition, and IR spectra.
The silicate radical of patynite is different from those of tokkoite and tinaksite [8,9] which have the stoichiometry [Si 7 O 18 (OH)] 9− and are built up by unbranched double chains of Si tetrahedra, which form eight-and four-membered rings ( Figure 11). The corrugated layers of Ca-octahedra in tokkoite and tinaksite is also topologically different ( Figure 12).
Based on the structural data described above, patynite can be considered as a prototype of a material with heteropolyhedral structure that is capable of the selective accumulation and immobilization of large cations in structural channels.
Supplementary Materials: The CIF file (containing all crystallographic information) and the hkl file (containing all hkl reflections) are available online at http://www.mdpi.com/2075-163X/9/10/611/s1. Author Contributions: V.S.L. collected the material in situ, A.V.K. found the new mineral; F.C. and F.N. performed the X-ray structural investigations; R.Š. and A.V.K. conducted the electron-microprobe analyses and obtained Raman spectrum; N.V.C. obtained IR spectrum and analyzed IR and Raman data; A.A.A. and D.I.B. determined the physical, chemical, and optical properties; A.V.K., F.C., N.V.C., and F.N. wrote the paper.
Funding: A part of this work (infrared spectroscopy and, partly, crystal-chemicalanalysis) was financially supported by the Russian Foundation for BasicResearch, grant no. 18-29-12007-mk.