Victor N. Yakovenchuk

Ivanyukite-Na-T, ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu: New microporous titanosilicates from the Khibiny massif (Kola Peninsula, Russia) and crystal structure of ivanyukite-Na-T

Abstract Ivanyukite-Na-T, Na3[Ti4(OH)O3(SiO4)3]·7H2O, ivanyukite-Na-C, Na2[Ti4O2(OH)2(SiO4)3]·6H2O, ivanyukite-K, K2[Ti4(OH)2O2(SiO4)3]·9H2O, and ivanyukite-Cu, Cu[Ti4(OH)2O2 (SiO4)3]·7H2O, are new microporous titanosilicates found in a natrolitized microcline-aegirine-sodalite lens in the orthoclase-bearing urtite at the Koashva Mountain (Khibiny Massif, Kola Peninsula, Russia). The minerals occur as well-shaped colorless (ivanyukite-Na-T), paleorange (ivanyukite-Na-C), pale-blue (ivanyukite-K), and green (ivanyukite-Cu) cubic crystals (up to 1.5 mm in diameter) grown on microcline, vinogradovite, sazykinaite-(Y), natrolite, and djerfisherite. The minerals have vitreous luster and white streak. They are transparent and non-fluorescent. The Mohs hardness is estimated as ~4. The minerals are brittle. Cleavage is perfect on {100} (ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu) or on {1011} (ivanyukite-Na-T), fracture is stepped. Density, measured by the sink/float method in heavy liquids, ranges from 2.60 (ivanyukite-Na-C) to 2.70 g/cm3 (ivanyukite-Na-T, ivanyukite-K, and ivanyukite-Cu), whereas calculated densities are: 2.58 (ivanyukite-Na-T), 2.39 (ivanyukite-Na-C), 2.69 (ivanyukite-K), and 2.46 g/cm3 (ivanyukite- Cu). Ivanyukite-Na-T is uniaxial (+), nω = 1.76(1), nε = 1.85(9) (589 nm), and the other minerals are isotropic, n = 1.73(1). Chemical analysis by electron microprobe gave (wt% for ivanyukite-Na-T, ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu, respectively): Na2O 7.46, 5.19, 0.27, and 0.17; Al2O3 0.07, 0.21, 0.18, and 0.07; SiO2 23.75, 25.47, 23.16, and 24.80; SO3 0.00, 0.00, 0.00, and 0.20; K2O 5.89, 6.34, 7.09, and 6.81; CaO 0.21, 0.14, 0.95, and 0.23; TiO2 38.89, 37.81, 36.14, and 38.36; MnO 0.05, 0.33, 0.68, and 0.28; FeO 0.54, 2.17, 0.37, and 0.73; CuO 0.00, 0.00, 2.21, and 6.81; SrO 0.00, 0.00, 0.19, and 0.00; Nb2O5 2.99, 2.90, 3.62, and 3.02; BaO 0.14, 0.00, 0.00, and 0.00; H2O (by the Penfield method) 19.00, 19.15, 25.00, and 21.50; total 98.99, 99.71, 99.86, and 98.97. The empirical formulae (based on Si+Al = 3 apfu) are (Na1.82 K0.95 Ca0.03 Ba0.01)Σ2.81[(Ti3.68 Nb0.17 Fe0.06 Mn0.01)Σ3.92(Si2.99 Al0.01)Σ3.00O14.59(OH)1.37]·7.29H2O (ivanyukite-Na-T), (Na1.17K0.94Ca0.03)Σ2.14[(Ti3.32Fe0.21Nb0.15Mn0.03)Σ3.71(Si2.97Al0.03)Σ3.00 O12.89(OH)2.87]·6.01H2O (ivanyukite-Na-C), (K1.16Cu0.21Ca0.13Na0.07Sr0.01)Σ1.58[(Ti3.49Nb0.21Mn0.07Fe0.04)Σ3.81(Si2.97Al0.03)Σ3.00 O13.19(OH)2.75]·9.32H2O (ivanyukite-K), and (Cu0.62K0.43Na0.04Ca0.03)Σ1.12[(Ti3.48Nb0.16Fe0.07Mn0.03)Σ3.74(Si2.99Al0.01)Σ3.00 O12.88(OH)2.88(SO4)0.02]·7.21H2O (ivanyukite-Cu). Ivanyukite-Na-T is trigonal, R3m, a = 10.94(2), c = 13.97(4) Å, Z = 3. Other minerals are cubic, P4̅3m a = 7.856(6) (ivanyukite-Na-C), 7.808(2) (ivanyukite-K), and 7.850(7) Å (ivanyukite-Cu); Z = 1. The strongest lines in the powder X-ray diffraction pattern [dbs(Å) (Iobs) hkl] are: 7.88(100) (011), 3.277(60)(014), 3.175(80)(212), 2.730(50)(220), 2.607(70)(303), 2.471(50)(124), 1.960(60)(044), 1.916(50) (135) (ivanyukite-Na-T); 7.88(100)(100), 4.53(30)(111), 3.205(80)(211), 2.774(30)(220), 2.622(40)(221, 300), 2.478(40)(310), 1.960(30)(400), 1.843(30)(330, 411) (ivanyukite-Na-C); 7.85(100)(100), 3.91(20)(200), 3.201(80) (211), 2.765(20)(220), 2.602(30)(221, 300), 2.471(40)(310), 1.951(30)(400), 1.839(30)(330, 411) (ivanyukite-K); 7.87(100)(100), 3.94(20)(200), 3.205(80)(211), 2.774(20)(220), 2.616(30)(221, 300), 2.481(30)(310), 1.960(30) (400), 1.843(30)(330, 411) (ivanyukite-Cu). The crystal structure of ivanyukite-Na-T [trigonal, R3m, a = 10.921(3), c = 13.885(4) Å, V = 1434.2(7) Å3] has been solved from highly mosaic crystal and refined to R1 = 0.147 on the basis of 723 unique observed reflections. The crystal structures of ivanyukite-group minerals are based upon a 3-dimensional framework of the pharmacosiderite type, consisting of four edge-sharing TiO6-octahedra interlinked by SiO4 tetrahedra. The framework has a 3-dimensional system of channels defined by 8-membered rings with an effective channel width of 3.5 Å (calculated as the distance between O atoms across the channels minus 2.7 Å). The channels are occupied by Na+ and K+ cations and H2O molecules. The infrared spectra of the ivanyukite group minerals show 14 absorption bands caused by vibrations of Si-O and Ti-O bonds, molecular water, and (OH)- groups. Ivanyukite-Na-T formed as a late-stage, hydrothermal phase of ultra-agpaitic hydrothermalites; ivanyukite-Na-C is produced by partial hydration of ivanyukite-Na-T, and both ivanyukite-K and ivanyukite-Cu are produced by partial hydration of ivanyukite-Na-T and natural cation exchange of Cu for Na near dissolved djerfisherite and chalcopyrite grains. Nomenclature of the ivanyukite group is based on the dominant extraframework cation and symmetry of the crystal structure. The minerals are named in honor of Gregory Yur’evich Ivanyuk, Russian mineralogist and petrologist, head of the Laboratory of Self-Organized Mineral Systems in the Geological Institute of the Kola Science Centre of the Russian Academy of Sciences, for his contributions to the petrology and mineralogy of banded iron-formations, alkaline, and alkaline-ultrabasic massifs.

Cafetite, Ca[Ti2O5](H2O): Crystal structure and revision of chemical formula

Abstract The crystal structure of cafetite, ideally Ca[Ti2O5](H2O), (monoclinic, P21/n, a = 4.9436(15), b = 12.109(4), c = 15.911(5) Å, b = 98.937(5)°, V = 940.9(5) Å3, Z = 8) has been solved by direct methods and refined to R1 = 0.057 using X-ray diffraction data collected from a crystal pseudo-merohedrally twinned on (001). There are four symmetrically independent Ti cations; each is octahedrally coordinated by six O atoms. The coordination polyhedra around the Ti cations are strongly distorted with individual Ti-O bond lengths ranging from 1.743 to 2.223 Å (the average bond length is 1.98 Å). Two symmetrically independent Ca cations are coordinated by six and eight anions for Ca1 and Ca2, respectively. The structure is based on [Ti2O5] sheets of TiO6 octahedra parallel to (001). The Ca atoms and H2O groups are located between the sheets and link them into a three-dimensional structure. The structural formula of cafetite confirmed by electron microprobe analysis is Ca[Ti2O5](H2O), in contrast to the formula (Ca,Mg)(Fe,Al)2Ti4O12 .4H2O suggested by Kukharenko et al. (1959). The wrong chemical formula suggested for cafetite by Kukharenko et al. (1959) is probably due to admixtures of magnetite or titanomagnetite in their samples. Cafetite is chemically related to kassite, CaTi2O4(OH)2, but differs from it in structure and structural formula.

3D mineralogical mapping of the Kovdor phoscorite–carbonatite complex (Russia)

The Kovdor baddeleyite–apatite–magnetite deposit in the Kovdor phoscorite–carbonatite pipe is situated in the western part of the zoned alkali-ultrabasic Kovdor intrusion (NW part of the Fennoscandinavian shield; Murmansk Region, Russia). We describe major intrusive and metasomatic rocks of the pipe and its surroundings using a new classification of phoscorite–carbonatite series rocks, consistent with the IUGS recommendation. The gradual zonation of the pipe corresponds to the sequence of mineral crystallization (forsterite–hydroxylapatite–magnetite–calcite). Crystal morphology, grain size, characteristic inclusions, and composition of the rock-forming and accessory minerals display the same spatial zonation pattern, as do the three minerals of economic interest, i.e. magnetite, hydroxylapatite, and baddeleyite. The content of Sr, rare earth elements (REEs), and Ba in hydroxylapatite tends to increase gradually at the expense of Si, Fe, and Mg from early apatite–forsterite phoscorite (margins of the pipe) through carbonate-free, magnetite-rich phoscorite to carbonate-rich phoscorite and phoscorite-related carbonatite (inner part). Magnetite displays a trend of increasing V and Ca and decreasing Ti, Mn, Si, Cr, Sc, and Zn from the margins to the central part of the pipe; its grain size initially increases from the wall rocks to the inner part and then decreases towards the central part; characteristic inclusions in magnetite are geikielite within the marginal zone of the phoscorite–carbonatite pipe, spinel within the intermediate zone, and ilmenite within the inner zone. The zoning pattern seems to have formed due to both cooling and rapid degassing (pressure drop) of a fluid-rich magmatic column and subsequent pneumatolytic and hydrothermal processes.

Chivruaiite, Ca4(Ti,Nb)5[(Si6O17)2[(OH,O)5]·13-14H2O, a new mineral from hydrothermal veins of Khibiny and Lovozero alkaline massifs

Abstract Chivruaiite is a new Ca titanosilicate [orthorhombic, Cmmm, a = 7.17(2), b = 22.98(9), c = 6.94(2) Å, V = 1144.4 Å3, Z = 1], chemically and structurally related to zorite. The mineral is found in three different hydrothermal veins within the Khibiny and Lovozero alkaline massifs, Kola Peninsula, Russia. It is associated with microcline, eudialyte, natrolite, astrophyllite, aegirine, etc. Chivruaiite occurs as elongate-prismatic crystals (up to 3 mm long) with {100}, {010}, {001}, {101}, and {011} as dominant faces, as well as radiating aggregates. The mineral is transparent, pale-pink to colorless, with vitreous luster and white streak. Cleavage is distinct on {100} and {010}; fracture is step-like. Mohs hardness is about 3. In transmitted light, the mineral is pale-pink, with a faint pleochroism: Z = pale-pink, on X and Y = colorless; dispersion r < v. Chivruaiite is biaxial (+): α =1.705(5), β = 1.627(2), γ = 1.612(2) (for λ = 589 nm), 2Vmeas = 40 ± 5°, 2Vcalc = 31.7°. Optical orientation: X = b, Y = a, Z = c, Dcalc = 2.42 g/cm3, Dmeas = 2.40.2.42 g/cm3. The mean chemical composition determined by electron microprobe is (wt%): SiO2 45.14; TiO2 20.63; Al2O3 0.07; Fe2O3 0.18; MnO 0.02; MgO 0.01; CaO 10.53; Na2O 0.10; K2O 1.30; SrO 0.28; Nb2O5 3.63; H2O 17.30; sum. 99.19. Empirical formula calculated on the basis of Si = 12 is (Ca3.00K0.44 Na0.05Sr0.04Mn0.01)Σ=3.54(Ti4.13Nb0.44Fe3+0.04 Al0.02)Σ=4.63[Si12O34 |(OH)4.51O0.49]·13.08H2O. Simplified formula is Ca4(Ti,Nb)5[(Si6O17)2|(OH,O)5]·13-14H2O. The strongest X-ray powder-diffraction lines [d in Å, (I), (hkl)] are 11.6 (100) (020), 6.91 (90) (110, 001), 5.23 (50) (130), 3.41 (50) (220), 3.35 (50) (061, 151), 3.04 (80) (221, 240). The structure of chivruaiite was refined to R1 = 0.038 on the basis of 687 unique observed reflections. It is based upon an open framework of SiO4 tetrahedra, TiO6 octahedra, and TiO5 pyramids. Framework cavities are occupied by Ca2+ and K+ cations, and H2O molecules. The mineral is named after its type locality in the Chivruai River valley (the Lovozero massif, Kola Peninsula, Russia). Chivruaiite is a Ca-analog of zorite and ETS-4 and is closely related to haineaultite.

Armbrusterite, K5Na6Mn3+Mn142+[Si9O22]4(OH)10·4H2O, a new Mn hydrous heterophyllosilicate from the Khibiny alkaline massif, Kola Peninsula, Russia

Abstract Armbrusterite, ideally K5Na6Mn3+Mn2+14[Si9O22]4(OH)10·4H2O, is a new silicate of potassium, sodium, and manganese found in a thin cancrinite-aegirine-microcline vein within urtite at Mt. Kukisvumchorr. The mineral occurs in intimate association with raite. Other associated minerals are lamprophyllite, mangan-neptunite, pectolite, vinogradovite, calcite, molybdenite, galena, sphalerite, and fluorite. Armbrusterite occurs as split, curved crystals and spherulites (≤2 mm diameter). The mineral is translucent (transparent in thin fragments), dark reddish-brown. It has vitreous luster and light-brown streak. Cleavage is perfect on (001) and the fracture is uneven. Mohs hardness is about 3.5. In transmitted light, the mineral is reddish-brown, with strong pleochroism: X = light yellowish-brown, Y and Z = dark reddish-brown; dispersion r > v, weak. Armbrusterite is biaxial (.): α = 1.532(2), β = 1.560(2), γ = 1.564(2) (for λ = 589 nm), 2V varies from 10° to 20°. Optical orientation: X is perpendicular to (001). The mean chemical composition determined by electron microprobe and the Penfield method (for H2O) is (wt%): Na2O 5.26, MgO 0.19, Al2O3 0.04, SiO2 56.02, K2O 6.13, CaO 0.26, TiO2 0.04, MnO 23.62, Mn2O3 2.07, FeO 0.65, ZnO 0.20, H2O 4.1, sum. 98.58. Empirical formula calculated on the basis of Si = 36 is K5.03Na6.55(Mn2+12.86Mn3+1.01Fe2+0.35Mg0.18 Ca0.18Zn0.09Al0.03Ti0.02)Σ=14.72[Si36O88](OH)10.10 ·3.75 H2O. Armbrusterite is monoclinic, C2/m, a = 17.333(2), b = 23.539(3), c = 13.4895(17) Å, β = 115.069(9)°, V = 4985.4(11) Å3, Z = 2. The strongest X-ray powder-diffraction lines are [d in Å, (I), (hkl)]: 12.28 (100) (001), 4.10 (10) (003), 3.562 (10) (113, 261), 3.260 (18) (114), 3.117 (13) (203), 3.077 (54) (004), 2.622 (10) (371). The crystal structure of armbrusterite was refined to R1 = 0.085 on the basis of 3960 unique observed reflections. The structure is based upon double silicate [Si9O22] layers consisting of 5-, 6-, 7-, and 8-membered tetrahedra rings. The layers are linked via octahedral sheets formed by Na and Mn octahedra. The interior of the double silicate layers is occupied by K+ cations and H2O molecules. The mineral is named in honor of Thomas Armbruster (b. 1950; University of Berne) for his outstanding contribution to structural mineralogy and crystallography, especially to the study of Mn-rich minerals.

Dehydration of the zeolite merlinoite from the Khibiny massif, Russia: an in situ temperature-dependent single-crystal X-ray study

Dehydration behaviour of the zeolite merlinoite, NaK11[Al12Si20O64]·15H2O, from the Khibiny massif (Russia) was studied by means of single-crystal X-ray diffraction conjoined with step-wise heating to 225 C. At room temperature merlinoite has the space group Immm with a = 14.0312(5), b = 14.2675(6), c = 10.0874(4) A, and V = 2019.40(14) A3. At 75 °C the merlinoite structure undergoes pronounced dehydration accompanied by a phase transition to a structure that has the space group P42/nmc and remains consistent at elevated temperature. A fully dehydrated phase occurs at 200 °C (at 225 °C: a = 13.341(4), b = 13.341(4), c = 9.707(4) A, V = 1727.7(12) A3). Dehydration-induced framework distortion and symmetry were found to be different from those observed for synthetic potassium merlinoite with the K11.5[Al11.5Si20.5O64]·15H2O composition.

Polezhaevaite-(Ce), NaSrCeF6, a new mineral from the Khibiny massif (Kola Peninsula, Russia)

Abstract Polezhaevaite-(Ce) NaSrCeF6 is a new member of the gagarinite mineral group [hexagonal, P63/m, a = 6.207(7) Å, c = 3.801(9) Å, V = 126.8(2) Å3, Z = 1]. It is found in a natrolitized microcline-aegirinesodalite lens within apatite-rich urtite at Mt. Koashva (Khibiny massif, Kola Peninsula, Russia) in association with аegirine, albite, arfvedsonite, astrophyllite, burbankite, catapleiite, chlorbartonite, djerfisherite, elpasolite, fluorapatite, fluorite, galena, hydroxylapatite, ilmenite, lamprophyllite, lorenzenite, leucophanite, microcline, natrolite, nepheline, orickite, pectolite, pyrochlore, sodalite, sphalerite, strontiofluorite, tainiolite, titanite, vinogradovite, and villiaumite. Polezhaevaite-(Ce) occurs as parallel and sheaf-like aggregates of extremely thin fibers (up to 1 mm long and <1 μm thick), which fill leaching voids within burbankite crystals in natrolite and mantles around partially dissolved burbankite crystals in intimate association with strontiofluorite. Polezhaevaite-(Ce) is translucent (transparent in separate fibers), snowy-white, with a silky luster (in aggregates) and a white streak. Cleavage is not observed; fracture is splintery (in aggregates). The Mohs hardness of individual crystals could not be determined and approaches 3 in aggregates. In transmitted light, the mineral is colorless, uniaxial positive: ε = 1.497(5), ω = 1.490(5) (for λ = 589 nm). Dcalc = 4.646 g/cm3, Dmeas = >4.2 g/cm-3. The mean chemical composition determined by electron microprobe is (wt%): Na 5.27, Ca 3.08, Sr 29.72, Ba 0.48, La 11.76, Ce 14.12, Pr 0.49, Nd 3.09, F 31.95, total 99.96. Empirical formula calculated on the basis of F = 6 apfu is: (Na0.82Ca0.18)Σ=1.00(Sr1.21Ce0.36La0.30Ca0.09Nd0.08Ba0.01)Σ=2.06F6 (charge imbalance is +0.05). Its simplified formula is NaSrCeF6. The strongest X-ray powder-diffraction lines [d in Å, (I), (hkl)] are: 5.416(40)(100), 3.120(100)(101, 110), 2.198(70) (201), 1.796(90)(121, 211, 300, 102), 1.554(30)(220), 1.173(70)(321, 231, 140, 410,132, 312, 113). The mineral is named in honor of Lyudmila Ivanovna Polezhaeva (b. 1935), a Russian expert in electron microprobe analysis of minerals for her contribution to the mineralogy of alkaline rocks

Where Are New Minerals Hiding? The Main Features of Rare Mineral Localization Within Alkaline Massifs

Alkaline and alkaline-ultrabasic massifs of the Kola Peninsula are unrestrained world’s leaders in mineral diversity. More than 700 mineral species have been found here, and more than 200 of them – for the first time in the world. Discoveries of new minerals within alkaline massifs of the Kola Peninsula started in nineteenth century from W. Ramsay’s expeditions in the Khibiny and Lovozero mountains (Ramsay 1890; Ramsay and Hackman 1893) when lamprophyllite and murmanite were described. In twentieth century, quantity of minerals firstly discovered here was increasing exponentially with time, and well-known monograph of A. Khomyakov “Mineralogy of hyperagpaitic alkaline rock” (1995) gave list of 109 new minerals from these massifs. Now list of minerals discovered in the Khibiny and Lovozero massifs includes 198 species and constantly grows on 5–10 minerals per year.

Ivanyukite-Group Minerals: Crystal Structure and Cation-Exchange Properties

Four microporous titanosilicates of the ivanyukite group: ivanyukite-Na-T, ivanyukite-Na-C, ivanyukite-K, and ivanyukite-Cu – were discovered in a natrolitized microcline-aegirine-sodalite vein within orthoclase-bearing urtite of the Koashva apatite deposit, Khibiny alklaine massif (Yakovenchuk et al. 2009). Ivanyukite-Na-T formed as a late-stage, hydrothermal phase resulting from alteration of lamprophyllite, whereas ivanyukite-Na-C, ivanyukite-K and ivanyukite-Cu are products of either cation exchange or hydration of ivanyukite-Na-T. It is noteworthy that crystals of ivanyukite-Cu were found in close association with corroded grains of djerfisherite and chalcopyrite (Ivanyuk et al. this book).

Eliseevite, Na1.5Li[Ti2Si4O12.5(OH)1.5]·2H2O, a new microporous titanosilicate from the Lovozero alkaline massif (Kola Peninsula, Russia)

Abstract Eliseevite, Na1.5Li[Ti2Si4O12.5(OH)1.5]∙2H2O, is a new microporous titanosilicate of the lintisitekukisvumite family [monoclinic, C2/c, a = 27.48(1), b = 8.669(4), c = 5.246(2) Å, β = 90.782(8)°, V = 1249.7(9) Å3, Z = 4]. The mineral is found in two different peralkaline veins in an ijolite-foyaite- malignite differentiated complex of the Lovozero alkaline massif, Kola Peninsula, Russia. At Mt. Alluaiv, eliseevite occurs in an aegirine-eudialyte-sodalite-microcline vein as long-prismatic to fibrous crystals (up to 2 mm long) growing in voids of natrolitized sodalite in close association with albite, analcime, catapleiite, chabazite-Ca, gmelinite-K, manganoneptunite, microcline, murmanite, and an ussingite. At Mt. Punkaruaiv, it is found within a ussingite-aegirine-microcline vein as longprismatic crystals (up to 0.8 mm long) in close association with chabazite-Ca, chkalovite, eudialyte, manganoneptunite, punkaruaivite, rhabdophane-(Ce), sodalite, sphalerite, and steenstrupine-(Ce). It is a late-stage, hydrothermal mineral formed as a result of alteration of murmanite. The mineral is transparent, pale creamy to colorless, with a vitreous luster and a white streak. Cleavage is perfect along {100}, fracture is splintery. Mohs hardness is about 5. In transmitted light, the mineral is colorless, biaxial (-): α = 1.665(2), β = 1.712(2), γ = 1.762(5) (for λ = 589 nm); Y = b, Z^a = 8-12°. Dispersion is medium, r < v. Dcalc = 2.706 g/cm3, Dmeas = 2.68(4) g/cm3. The mean chemical composition (n = 7) determined by the Penfield method (water), ICP-MS (Li), and electron microprobe (other elements) is (wt%): H2O 10.50, Li2O 2.85, Na2O 9.15, K2O 0.08, CaO 0.05, Fe2O3 0.21, Al2O3 0.08, SiO2 46.87, TiO2 29.40, Nb2O5 0.72, total 99.91. The empirical formula calculated on the basis of Si = 4 apfu is: (Na1.51K0.01Ca0.01)Σ1.53Li0.98[(Ti1.89Nb0.03Fe3+0.01Al0.01)Σ1.94Si4O12.26(OH)1.74]∙2.12H2O. The simplified formula taking into account the results of a single-crystal study is Na1.5Li{Ti2O2[Si4O10.5(OH)1.5]}∙2H2O. The six strongest reflections in the X‑ray powder-diffraction pattern [d in Å, (I), (hkl)] are: 13.76(100) (200), 6.296(60)(310), 3.577(80)(710), 3.005(70)(421), 2.881(70)(910), 2.710(50)(621). The mineral is named in honor of Nikolai Aleksandrovich Eliseev (1897-1966), a remarkable Russian geologist and petrologist, Professor at Leningrad State University, for his contributions to the geology and petrology of metamorphic and alkaline complexes.