ALBERT

Description: Olenitic tourmaline with high amounts of tetrahedral B (up to 2.53 [4] B pfu) has been synthesized in a piston-cylinder press at 4.0 GPa, 700 °C, and a run duration of 9 days. Crystals are large enough (up to 30 x 150 μm) to allow for reliable and spatially resolved quantification of B by electron microprobe analysis (EMPA), single-crystal X-ray diffraction, and polarized single-crystal Raman spectroscopy. Tourmalines with radial acicular habit are zoned in [4] B-concentration [core: 2.53(25) [4] B pfu; rim: 1.43(15) [4] B pfu], whereas columnar crystals are chemically homogeneous [1.18(15) [4] B pfu]. An amount of 1.4(1) [4] B pfu was found in the columnar tourmaline by single-crystal structure refinement (SREF) ( R = 1.94%). The EMPA identify [T] Si –1 [V,W] O –1 [T] B 1 [V,W] (OH) 1 as the main and [X] –1 [T] Si –1 [X] Na 1 [T] B 1 as minor exchange vectors for [4] B-incorporation, which is supported by the SREF. Due to the restricted and well-defined variations in chemistry, Raman bands in the OH-stretching region (3000–3800 cm –1 ) are unambiguously assigned to a specific cation arrangement. We found the sum of the relative integrated intensity ( I rel ) of two low-frequency bands at 3284–3301 cm –1 (1) and 3367–3390 cm –1 (2) to positively correlate with the [4] B concentrations: [4] B [pfu] = 0.03(1) x [ I rel (1) + I rel (2)]. Hence, those bands correspond to configurations with mixed Si/B occupancy at the T site. Our semi-quantitative correlation also holds for well-characterized natural [4] B-bearing tourmaline from the Koralpe, Austria. This work shows the potential for Raman spectroscopy as a non-destructive method for the chemical classification of (precious) natural tourmaline, and as a tool to rapidly characterize chemical zonation of tourmalines in thin section.

Description: Distinctly chemically zoned tourmaline was found in a quartz vein near Tisovec, Slovak Ore Mountains, Slovakia. The tourmaline forms radial aggregates of light grey to green thin prismatic to acicular crystals growing in cracks in the host rock. The root zone of the aggregates has dravitic to oxy-dravitic compositions, shifting to magnesio-foitite in the middle parts of the crystals and to foititic compositions in the outer parts of the aggregates. The optimized formula, considering the single-crystal structure refinement (SREF) and the chemistry of the magnesio-foititic zone, is ~ X ( 0.5 Na 0.4 Ca 0.1 ) Y (Mg 1.1 Al 1.0 Fe 2+ 0.8 Fe 3+ 0.1 ) Z (Al 5.7 Fe 3+ 0.3 ) (Si 5.9 Al 0.1 O 18 ) (BO 3 ) 3 (OH) 3 [O 0.6 (OH) 0.3 F 0.1 ], with lattice parameters (SREF) a 15.929(2) Å, c 7.163(1) Å, and V 1574.0(7) Å 3 . SREF data as well as a detailed study of bond lengths indicate a dominancy of Al 3+ at the Z site substituted by a small proportion of Fe 3+ , while Fe 2+ and Mg 2+ essentially occupy the Y site along with a significant amount of Al. The chemical composition is controlled by the substitutions FeMg –1 , Al(Fe,Mg) –1 Na –1 , and AlO(Fe,Mg) –1 (OH) –1 . The AlO(Fe,Mg) –1 (OH) –1 substitution is dominant in the transition from oxy-dravite to magnesio-foitite, and the Al(Fe,Mg) –1 Na –1 substitution prevails in the magnesio-foitite and foitite compositions. Both proton- and alkali-deficient substitutions produce the enrichment in Al which can be linked to the forming of the acicular habit. Aluminum strongly prefers the Z -site, whose octahedra form a network of chains parallel to c . Consequently, polymerization of the Z O 6 octahedral network will dominate growth in the a direction. Therefore, the chemical composition, mainly Al enrichment, which is common for most of the acicular to fibrous tourmalines, can be an important factor promoting preferential growth in the c direction. The rate and time for crystallization, which depend mostly on the temperature and cooling rate, are also factors which should be considered.

Description: A synthetic Cu-rich tourmaline crystal (Lebedev et al. 1988) consists of three different zones. Each zone was characterized by EMPA, SIMS, and single-crystal structure refinement (SREF). The first zone (which crystallized directly on the seed crystal) has the formula ~ X (Na 0.8 0.2 ) Y (Al 2.0 Cu 0.9 0.1 ) Z Al 6 T (Si 5.1 Al 0.9 )O 18 (BO 3 ) 3 V (OH) 3 W [O 0.7 F 0.2 (OH) 0.1 ] with lattice parameters a 15.835(1), c 7.093(1) Å ( R = 2.4%). The second zone has the formula ~ X (Na 0.8 0.2 ) Y (Al 1.8 Cu 1.1 0.1 ) Z Al 6 T (Si 5.1 Al 0.7 B 0.2 )O 18 (BO 3 ) 3 V (OH) 3 W [(OH) 0.4 F 0.3 O 0.3 ] with a 15.824(1), c 7.087(1) Å ( R = 2.3%). The third zone (highest Cu content with ~14 wt.% CuO) has the formula X (Na 0.81 0.19 ) Y (Cu 1.72 Al 1.21 0.07 ) Z (Al 5.96 Cu 0.04 ) (BO 3 ) 3 T (Si 5.17 Al 0.48 B 0.35 )O 18 V (OH) 3 W [(OH) 0.63 F 0.37 ] with a 15.849(1), c 7.087(1) Å ( R = 2.5%). While [4] Al decreases from zone 1 to zone 3, [4] B increases (by chemistry and SREF), which could be explained by a decreasing temperature during tourmaline crystallization. Such a T -site occupancy is in agreement with the 〈 T –O〉 distance, which strictly monotonically decreases from 1.625(1) to 1.616(1) Å. We suggest that very small amounts of Cu are present at the Z site of all investigated tourmaline samples, but only in the Cu-richest zone (~14 wt.% CuO) is the refined value for Cu at the Z site (~1% of the total Cu) higher than the 3 error. The Y O 6 octahedron of this Cu-richest known tourmaline is mainly occupied by Cu. Two of the six ( Cu ,Al)–O distances are significantly enlarged: Y –O1 with 2.031(2) Å and Y –O3 with 2.170(2) Å, while the other distances Y –O2 and Y –O6 with ~1.951(2) Å are significantly smaller. The proportion of the average of the two enlarged distances to the average of the other distances in the Cu-richest zone gives a value of ~1.08, which is the highest value known so far for Cu-bearing tourmalines. We conclude that for the Cu-richest zone the Jahn-Teller effect appears to be verified.

Description: Bosiite, NaFe 3+ 3 (Al 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, is a new mineral species of the tourmaline supergroup from the Darasun gold deposit (Darasun mine), Vershino-Darasunskiy, Transbaikal Krai, Eastern-Siberian Region, Russia (52°20'24''N, 115°29'23''E). Bosiite formed as a hydrothermal phase in a gold-bearing quartz-vein spatially related to the Amudzhikan–Sretensky subvolcanic K-rich granodiorite-porphyry intrusion. Ores of this deposit are enriched in sulfides (up to 60%). Bosiite is intimately associated with other tourmalines. The first tourmaline generation is bosiite, which is followed by a second generation of oxy-dravite and a third generation of dravite. Bosiite also coexists with quartz and pyrite; further associated minerals in the vein are gangue minerals (quartz, calcite, and dolomite), sulfides (pyrite, arsenopyrite, chalcopyrite, pyrrhotite, tetrahedrite, sphalerite, and galena) and native gold. Crystals of bosiite are dark brown to black with a pale-brown streak. Bosiite is brittle and has a Mohs hardness of 7; it is non-fluorescent, has no observable parting and cleavage. It has a measured density of 3.23(3) g/cm 3 (by pycnometry) and a calculated density of 3.26(1) g/cm 3 . In plane-polarized light, it is pleochroic, O = yellow-brown, E = red-brown. Bosiite is uniaxial negative, = 1.760(5), = 1.687(5). The mineral is trigonal, space group R 3 m , a = 16.101(3), c = 7.327(2) Å, V = 1645.0(6) Å 3 . The eight strongest X-ray diffraction lines in the (calculated) powder pattern [ d in Å( I ) hkl ] are: 2.606(100)(50-1), 8.051(58)(100), 3.008(58)(3-1-2), 4.025(57)(4-20), 3.543(50)(10-2), 4.279(46) (3-11), 2.068(45)(6-1-2), 4.648(28)(300). Analysis by a combination of electron microprobe (EMPA), inductively coupled plasma mass spectrometry (ICP-MS), Mössbauer spectroscopic data and crystal-structure refinement results in the empirical structural formula: \[ \begin{array}{c}{}^{X}{\left({\mathrm{Na}}_{0.73}{\mathrm{Ca}}_{0.23}{\square }_{0.04}\right)}_{\mathrm{\Sigma }1.00}{}^{Y}{\left({\mathrm{Fe}}^{3+}{}_{1.47}{\mathrm{Mg}}_{0.80}{\mathrm{Fe}}^{2+}{}_{0.59}{\mathrm{Al}}_{0.13}{\mathrm{Ti}}^{4+}{}_{0.01}\right)}_{\mathrm{\Sigma }3.00}{}^{Z}{\left({\mathrm{Al}}_{3.23}{\mathrm{Fe}}^{3+}{}_{1.88}{\mathrm{Mg}}_{0.89}\right)}_{\mathrm{\Sigma }6.00}\\\relax {}^{T}{\left({\mathrm{Si}}_{5.92}{\mathrm{Al}}_{0.08}{\mathrm{O}}_{18}\right)}_{\mathrm{\Sigma }6.00}{\left({\mathrm{BO}}_{3}\right)}_{3}{}^{V}{\left(\mathrm{OH}\right)}_{3}{}^{W}{\left[{\mathrm{O}}_{0.85}{\left(\mathrm{OH}\right)}_{0.15}\right]}_{\mathrm{\Sigma }1.00}\end{array} \] According to the IMA-CNMNC guidelines, the dominant valence at the Y site is 3+ and the dominant cation is Fe 3+ . To accommodate the disorder and allocating cations to the Z and Y sites, the recommended procedure leads to the optimized empirical formula (based on 31 O): X (Na 0.73 Ca 0.23 0.04 ) Y (Fe 3+ 2.40 Fe 2+ 0.59 Ti 4+ 0.01 ) Z (Al 3.36 Mg 1.69 Fe 3+ 0.95 ) T (Si 5.92 Al 0.08 O 18 ) (BO 3 ) 3 V (OH) 3 W [O 0.85 (OH) 0.15 ]. Bosiite, ideally NaFe 3+ 3 (Al 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, is related to end-member povondraite, ideally NaFe 3+ 3 (Fe 3+ 4 Mg 2 )(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, by the substitution Z Al 4 -〉 Z Fe 3+ 4 . Further, bosiite is related to oxy-dravite, ideally Na(Al 2 Mg)(Al 5 Mg)(Si 6 O 18 )(BO 3 ) 3 (OH) 3 O, by the substitutions [6] Fe 3+ 3 -〉 [6] Al 3 . Bosiite is named after Dr. Ferdinando Bosi, researcher at the University of Rome La Sapienza, Italy, and an expert on the crystallography and mineralogy of the tourmaline-supergroup minerals and the spinels.

Description: A monoclinic (2 M ) polytype of sideronatrite, Na 2 Fe(SO 4 ) 2 (OH)(H 2 O) 3 , was found at Xitieshan, Qinghai Province, China. The crystal structure was solved by direct methods and refined by full-matrix least-squares ( R 1 = 3.88 %) in the space group P 12 1 / n 1 with a = 7.1559(14), b = 7.2845(15), c = 20.889(4) Å, β = 99.37(3)°, V = 1074.4(4) Å 3 , and Z = 4, using 2207 observed reflections with I 〉 2( I ). The atomic arrangement of sideronatrite-2 M confirms a theoretical model in space group P 2 1 / a , previously proposed in literature. The structure of sideronatrite-2 M is based on ferric-sulfate chains of 7 Å periodicity, similar to those observed in the structures of the orthorhombic polytype and of metasideronatrite. The system of hydrogen bonds has been determined.

Description: 〈span〉The crystal structures of coquimbite and paracoquimbite from the Hongshan Cu–Au deposit, NW China, were refined by single-crystal X-ray diffraction, including the positions of all non-H atoms and hydrogen atoms.The unit-cell parameters of coquimbite are 〈span〉a〈/span〉 = 10.9644(15), 〈span〉c〈/span〉 = 17.090(3) Å, and 〈span〉V〈/span〉 = 1769.6(5) Å〈sup〉3〈/sup〉, 〈span〉Z〈/span〉 = 4 with space group 〈span〉P〈/span〉3¯1〈span〉c〈/span〉. The crystal structure was refined based on 1352 unique reflections to 〈span〉R〈/span〉1(〈span〉F〈/span〉) = 0.0301, yielding the formula Fe〈sub〉1.64〈/sub〉Al〈sub〉0.36〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉∙9H〈sub〉2〈/sub〉O. Among the three cation positions of coquimbite, the isolated octahedral one is dominantly occupied by Al, 〈span〉i.e.〈/span〉 Al〈sub〉0.660(3)〈/sub〉Fe〈sub〉0.340(3)〈/sub〉. Consequently, the average Al–O interatomic distance is 1.9155 Å, smaller than the Fe–O distances, 2.002 Å for Fe(1), and 1.989 Å for Fe(2). Based on the structure data available for coquimbite in the literature, the ideal formula should be expressed as AlFe〈sub〉3〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉6〈/sub〉·18H〈sub〉2〈/sub〉O (〈span〉Z〈/span〉 = 2) or Fe〈sub〉2−〈span〉x〈/span〉〈/sub〉Al〈sub〉〈span〉x〈/span〉〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉·9H〈sub〉2〈/sub〉O, 〈span〉x〈/span〉 ∼ 0.5 rather than Fe〈sup〉3+〈/sup〉〈sub〉2〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉∙9H〈sub〉2〈/sub〉O. The simplified formula for coquimbite from Hongshan is (Al〈sub〉0.66〈/sub〉Fe〈sub〉0.34〈/sub〉)Fe〈sub〉3〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉6〈/sub〉·18H〈sub〉2〈/sub〉O.The unit-cell parameters of paracoquimbite are 〈span〉a〈/span〉 = 10.9631(16), 〈span〉c〈/span〉 = 51.473(10) Å, and 〈span〉V〈/span〉 = 5357.7(15) Å〈sup〉3〈/sup〉, 〈span〉Z〈/span〉 = 12 with space group 〈span〉R〈/span〉3¯. The crystal structure was refined using 2733 unique reflections to 〈span〉R〈/span〉1(〈span〉F〈/span〉) = 0.0550, which led to the formula Fe〈sub〉1.91〈/sub〉Al〈sub〉0.09〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉3〈/sub〉∙9H〈sub〉2〈/sub〉O. There are five non-equivalent octahedrally coordinated metal sites for Fe in the structure of paracoquimbite. The range of Fe〈sup〉[6]〈/sup〉–O interatomic distances in paracoquimbite (1.966 Å–2.016 Å) can well be compared with those found in various sulfate minerals of ferric iron.Both minerals are characterized by a complex system of hydrogen bonds involving three types of H〈sub〉2〈/sub〉O molecules, respectively: those of [Fe〈sub〉3〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉6〈/sub〉(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉]〈sup〉3−〈/sup〉 clusters, of isolated [Fe(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉]〈sup〉3+〈/sup〉 or [Al(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉]〈sup〉3+〈/sup〉 octahedra and further interstitial (H〈sub〉2〈/sub〉O) groups. The interstitial H〈sub〉2〈/sub〉O molecules resemble a cyclohexane-like chair and are held in the structure solely by hydrogen bonding. In coquimbite H〈sub〉2〈/sub〉O〈sub〉W〈/sub〉(2) is disordered with two alternative orientations (H2B1 and H2B2), in paracoquimbite interstitial H〈sub〉2〈/sub〉O consists of two H〈sub〉2〈/sub〉O molecules, H〈sub〉2〈/sub〉O〈sub〉W〈/sub〉(3) and H〈sub〉2〈/sub〉O〈sub〉W〈/sub〉(4). The range of the O–H stretching frequencies between ∼2750 and ∼3650 cm〈sup〉−1〈/sup〉 from infrared spectroscopy for paracoquimbite is in fair accordance with the calculated values between ∼2874 and ∼3600 cm〈sup〉−1〈/sup〉 from both the 〈span〉d〈/span〉(O…O) lengths and the 〈span〉d〈/span〉(H…O) lengths.〈/span〉

Description: Cairncrossite is a new phyllosilicate species found in manganese ore on dumps of the Wessels Mine, Kalahari Manganese Field, South Africa. Associated minerals are richterite, sugilite, lizardite and fibrous pectolite. It occurs as radiating platy micaceous aggregates of up to 1 cm in size. Cairncrossite is colourless, appearing white, and the crystals are translucent to transparent with a white streak and vitreous to pearly lustre. The crystals are sectile before brittle fracture, with a Mohs hardness of 3. A perfect cleavage parallel (001) is observed. The calculated density is 2.486 g cm –3 . The mineral is biaxial positive with n α = 1.518(2), n β = 1.522(2), n = 1.546(2), 2 V obs = 33.9(6)° (2 V calc = 44.97°) at 589.3 nm and 24°C. The orientation of the indicatrix is Z ^ c * = 10°. The dispersion is weak ( r 〈 v ) and no pleochroism is observed. An intense light-blue fluorescence is emitted under shortwave UV radiation. Cairncrossite is triclinic, space group P $$\overline{1}$$ , a = 9.6265(5), b = 9.6391(5), c = 15.6534(10) Å, α = 100.89(1), β = 91.27(1), = 119.73(1)°, V = 1227.08(13) Å 3 , Z = 1. The strongest lines in the Gandolfi X-ray powder-diffraction pattern [ d in Å( I )( hkl )] are 15.230 (100)(001), 8.290 (15)(1–10), 5.080(25)(003), 3.807(30)(004), and 3.045(20)(005). The chemical composition obtained by electron-microprobe analysis is Na 2 O 3.06, K 2 O 0.11, CaO 18.61, SiO 2 54.91, SrO 11.75, total 88.44 wt%. The relevant empirical formula, based on 16 Si atoms per formula unit ( apfu ) and TGA data is: Sr 1.99 K 0.02 Ca 5.81 Na 1.73 Si 16 O 55.84 H 30.33 . Taking variable sodium contents into account, the idealized structural formula is Sr 2 Ca 7–x Na 2x (Si 4 O 10 ) 4 (OH) 2 (H 2 O) 15–x with 0 ≤ x ≤ 1, and the simplified formula for sodium-rich crystals is SrCa 3 Na(Si 4 O 10 ) 2 (OH)(H 2 O) 7 with Z = 2. The structure of cairncrossite was refined on single-crystal X-ray data (Mo K α radiation) to R 1 = 0.047. Cairncrossite belongs to the gyrolite and reyerite mineral groups, it is characterized by sheets consisting of edge-sharing CaO 6 octahedra, which are corner-linked on both sides to silicate layers. These units are intercalated by layers formed by SrO 8 polyhedra, which are arranged in pairs via a common edge, and further bound to disordered NaO 6 polyhedra. A complex system of hydrogen bonds strengthens the linkage to adjacent silicate layers. Cairncrossite exhibits a two-phase endothermic weight loss of the H 2 O molecules in the range 25–400°C; however, the mineral shows a nearly complete rehydration capability up to 400°C. The new mineral is named in honour of Bruce Cairncross, Professor and Head of the Department of Geology, University of Johannesburg.

Description: The crystal structures of the secondary ferric iron minerals kamarizaite, Fe 3 3+ (AsO 4 ) 2 (OH) 3 · 3H 2 O, and tinticite, Fe 3 3+ (PO 4 ) 2 (OH) 3 · 3H 2 O, for which highly contradictory data on crystal symmetry were reported, were studied by a combination of single-crystal X-ray diffraction and Rietveld refinement (supplemented by chemical analyses and thermogravimetry), using type material of both species and additional samples from several other localities, including the type localities. The previously unknown crystal structure of kamarizaite was determined from single-crystal intensity data (Mo K α, 293 K, R ( F ) = 2.91 %; all H atoms detected) using a sample from the Le Mazet vein, Échassières, Auvergne, France. The mineral is triclinic, space group $$P\overline{1}$$ (no. 2), with a = 7.671(2), b = 8.040(2), c = 10.180(2) Å, α = 68.31(3), β = 75.35(3), = 63.52(3)°, V = 519.3(2) Å 3 , Z = 2. Rietveld analyses of fine-grained kamarizaite collected underground at two different spots in Lavrion, Greece (Hilarion and Jean Baptiste areas) confirmed the structure model. Rietveld analyses of fine-grained tinticite from Tintic, Utah (USA), Bruguers (Spain) and Weckersdorf (Germany) demonstrate that kamarizaite and tinticite are triclinic and isotypic. A previously published structure model for tinticite, as well as the originally reported orthorhombic symmetry for kamarizaite, are shown to be incorrect. Refined unit-cell parameters of a cotype tinticite specimen from Tintic are: a = 7.647(1), b = 7.958(1), c = 9.987(1) Å, α = 67.90(1), β = 76.10(1), = 64.10(1)°, V = 504.4(2) Å 3 . Bruguers and Weckersdorf tinticite have very similar parameters. The common atomic arrangement is characterised by three unique, octahedrally coordinated Fe sites (on which Fe may be partially replaced by minor Al), two unique tetrahedrally coordinated T (As or P) sites, eight O, three O h , three O w and nine H sites. The topology features zig-zag chains along $$\left[\overline{1}10\right]$$ of dimers built of two edge-sharing FeO 6 octahedra corner-linked by a third FeO 6 octahedron. The chains are corner-linked by the T O 4 tetrahedra thus establishing a mixed octahedral-tetrahedral framework with a T :Fe ratio of 0.67, a pronounced layered arrangement parallel to (001) and narrow channels along [010]. Medium-strong to weak hydrogen-bonds provide additional strengthening of the structure. The topology is closely related to that of the recently described, triclinic aluminium phosphate afmite.

Description: The new mineral calciomurmanite, (Na,) 2 Ca(Ti,Mg,Nb) 4 [Si 2 O 7 ] 2 O 2 (OH,O) 2 (H 2 O) 4 , a Na-Ca ordered analogue of murmanite, was found in three localities at Kola Peninsula, Russia: at Mt. Flora in the Lovozero alkaline complex (the holotype) and at Mts. Eveslogchorr (the cotype) and Koashva, both in the Khibiny alkaline complex. Calciomurmanite is a hydrothermal mineral formed as a result of late-stage, low-temperature alteration (hydration combined with natural cation exchange) of a high-temperature, anhydrous phosphate-bearing titanosilicate, most likely lomonosovite and/or betalomonosovite, in the peralkaline (hyperagpaitic) rocks. The holotype sample is associated with microcline, aegirine, lorenzenite and fluorapatite, whereas the cotype sample occurs with microcline, aegirine, lamprophyllite, tsepinite-Ca and tsepinite-K. The mineral occurs as lamellae up to 0.1 x 0.4 x 0.6 cm, sometimes combined in fan-shaped aggregates up to 3.5 cm. Calciomurmanite is pale brownish or purple; the streak is white. The lustre is nacreous on cleavage surface and greasy on broken surface across cleavage. The (001) cleavage is perfect, mica-like; the fracture is stepped. D meas = 2.70(3), D calc = 2.85 g cm –3 . The mineral is optically biaxial (–), α = 1.680(4), β = 1.728(4), = 1.743(4), 2 V meas = 58(5)°. The IR spectrum is reported. The chemical composition (wt%, electron-microprobe data, H 2 O by the Alimarin method) is: Na 2 O 5.39, K 2 O 0.30, CaO 7.61, MgO 2.54, MnO 2.65, FeO 1.93, Al 2 O 3 0.85, SiO 2 30.27, TiO 2 29.69, Nb 2 O 5 6.14, P 2 O 5 0.27, H 2 O 11.59, total 99.23. The empirical formula of the holotype sample, calculated on the basis of Si + Al = 4 apfu , is: Na 1.34 Ca 1.04 K 0.05 Mg 0.49 Mn 0.29 Fe 0.21 Nb 0.36 Ti 2.85 (Si 3.87 Al 0.13 ) 4 O 16.40 (OH) 1.60 (PO 4 ) 0.03 (H 2 O) 4.94 . Calciomurmanite is triclinic, P -1, a = 5.3470(6), b = 7.0774(7), c = 12.146(1) Å, α = 91.827(4), β = 107.527(4), = 90.155(4)°, V = 438.03(8) Å 3 and Z = 1. The strongest reflections of the X-ray powder pattern [ d ,Å( I )( hkl )] are: 11.69(100)(001), 5.87(68)(011, 002), 4.25(89) (–1–11, –111), 3.825(44)(–1–12, 003, –112), 2.940(100)(–1–21, –121), 2.900(79)(004, 120). The crystal structure was solved by direct methods from single-crystal low-temperature (200 K) X-ray diffraction data and refined to R = 0.0656 for the holotype and 0.0663 for the cotype. The structure is based on a three-sheet HOH block: an octahedral ( O ) sheet containing alternating chains of NaO 6 and TiO 6 octahedra and two heteropolyhedral ( H ) sheets consisting of Si 2 O 7 groups, TiO 6 octahedra and CaO 8 polyhedra. H 2 O molecules occupy two sites in the interlayer space.