List of articles

Investigation of some new crystal strucuture type of phosphate minerals
under hydrothermal condition

Un Monophosphate Syntetique de Sodium et de Cobalt: Na4Co7(PO4)6

Dilshat Kobashi, Sizuo Kohara, Junji Yamakawa et Akira Kawahara

Acta Crystallographica C54, pp.7--9, (1998)

Tetrasodium heptacobalt hexaphosphate, a new monophosphate prepared by hydrothermal methods, comprises CoO6 and CoO4 coordination polyhedra connected to each other by corner and edge sharing to form zigzag layers parallel to the ab plane. These layers are interconnected by Co-O polyhedra and P-O tetrahedra via cprmer shareing to form a theree-dimensional network. The Na+ ions are located in the tunnels running parallel to the a axis.

Structure d'un Diphosphate Synthetique de Cobalt: Co2P2O7

Dilshat Kobashi, Sizuo Kohara, Junji Yamakawa et Akira Kawahara

Acta Crystallographica C53, pp.1532--1525, (1997)

The title compound, a new polymorphic phase of dicobalt diphosphate, Co2P2O7 was prepared by hydrothermal methods. The structure contains CoO6 coordination octahedra and P2O7 groups. The CoO6 octahedra are connected by edge sharing to form six-memberd rings, which are further interconnected to form two-dimensional zigzag sheets parallel to (001). The P2O7 groups link these sheets to build three-dimensional networks.

Synthetic Magnesium Sodium Hydrogen Monophosphate: MgNa3H(PO4)2

Akira Kawahara, Junji Yamakawa, Tadaoki Yamada and Dilshat Kobashi

Acta Crystallographica C51, pp.2220--2222, (1995)

The structure belongs to the monophosphate group and contains one type of PO4 tetrahedra connected to one type of MgO6 octahedra by corner sharing. These PO4-MgO6 groups are connected along the two shorter a and b axes to form two-dimantional zigzag sheets. Two sheets are connected along the longer c axis by two type of Na-O polyhedra. Pairs of PO4 tetrahedra in the sheets are connected by H atoms situated at the centres of symmetry, forming short hydrogen bonds.

Crystal structure of synthetic zinc monophosphate Zn2(OH)PO4.
A polymorph of tarbuttite

Akira Kawahara, Hiromi Moritani and Junji Yamakawa

Mineralogical Journal, Vol. 17, No.3, pp.132-139, (1994)

The syntheses of zinc hydroxyl monophosphate Zn2(OH)PO4 were carried out under hydrothermal conditions of 573 K and 200 kg/cm2. The Crystal data are: orthorhombic, P21212, a=8.099(1), b=8.325(1) and c=5.966(1) A. The structure was solved by three dimensional Patterson syntheses and refined by least squares methods to give a final residual index of R=0.042. There are four units of Zn2(OH)PO4 in a unit cell and three kinds of zinc atoms with different coordinations, where the first zinc atom is six-coordinated by six oxygen atoms and the third one is five-coordinated by four oxygen atoms and one hydroxyl group forming distorted pyramids. The framework consists of infinite straight chains of Zn-O ocrahedra along c-axis, connected together by isolated PO4. tetrahedra and distorted Zn-O pyramids. This compound is a polymorph of tarbuttite.

Un Monophosphate de Magnesium et de Sodium

J. Yamakawa, T. Yamada et A. Kawahara

Acta Crystallographica C50, pp.986-988, (1994)

The title compound, magnesium sodium phosphate, Mg5Na2(PO4)4, belongs to a group of monophosphates wich are constructed from five kinds of coordination polyhedra: two kinds of PO4 tetrahedra are connected by one type of Mg-O octahedra situated at the centres of symmetry; distorted five-coordinated Mg-O polyhedra and another type of distorted Mg-O octahedra are in general positions. Na-O polyhedra occupy the cavities formed by these five types of coordination polyhedra. The density, Dx of this compound is 3.00 Mg/m3, reflecting the high-pressure synthesis. Similar compounds precipitated at 1 atm. (101.325 kPa) have densitites of 2.55-2.82 Mg/m3, corresponding to the lower pressure condition.

Refinement of the Structure of Synthetic Sodium Zinc Monophosphate

J.Yamakawa, I.Watanabe and A.Kawahara

Acta Crystallographica C50, pp.979-980, (1994)

The title structure, Zn2NaH(PO4)2, belongs to the monophosphate group and contains two kinds of PO4 tetrahedra connected by two kinds of ZnO4 distorted tetrahedra. These four kinds of tetrahedra are connected by corner sharing to form sheets parallel to the ac plane. The PO4 tetrahedra are isolated from each other in the sheets. The Na and H atoms are located between the sheets. The Na atoms have six O atoms as nearest neighbours. The H atoms are connected to the apex O atoms of two adjacent sheets by hydrogen bonding.

Structure du Monophosphate Synthetique de Cuivre et de Sodium

A. Kawahara, T. Kageyama, I.Watanabe et J.Yamakawa

Acta Crystallographica C49, pp.1275--1277, (1993)

The structure of copper sodium monophosphate is built from two kinds of Cu atoms occupying the centres of symmetry of a dsp2 square plane of O atoms, with two additional O atoms; these two Cu--O octahedra are linked by edge sharing to form chains parallel to the a axis. The PO4 tetrahedra and Na--O polyhedra connect these Cu--O chains. The structure is another polymorph of \alpha-NaCuPO4. The former was synthesized at 2000 kg/cm2 (\sim 2 x 10 5 kPa pressure) and 773 K, resulting in a structure of high density (dx=3.61Mg /m3), 10 2 kPa, 1023 K); this may explain the fact that the PO4 tetrahedra of the former are more distorted than those of the latter.

Syntheses and/or Crystal structure analyses of minerals

Mineral Chemistry of schulenbergite and its Zn-dominant analogue from the Hirao mine, Osaka, Japan

Masayuki Ohnishi, Isao Kusachi, shoichi Kobayashi and Junji Yamakawa

Journal of Mineralogical and Petrological Sciences, J-STAGE Advence Publication, June 8, (2007)

Numanoite, Ca4CuB4O6(OH)6(CO3)2, A new mineral species,The Cu analogue of borcarite from the Fuka mine, Okayama prefecture, Japan

Masayuki Ohnishi, Isao Kusachi, Shoichi Kobayashi, Junji Yamakawa, Mitsuo Tanabe, Shigetomo Kishi and Takashi Yasuda

Canadian Mineralogist, Vol. 45, pp307-315 (2007)

Inyoite from Fuka, Okayama Prefecture, Japan

Isao Kusachi, Shoichi Kobayashi, Mitsuo Tanabe, Shigetomo Kishi and Junji Yamakawa

Journal of Mineralogical and Petrological Sciences, Vol. 99, pp67-71 (2004)

Ramsbeckite from the Hirao mine at Minoo, Osaka, Japan

Masayuki Ohnishi, Shoichi Kobayashi, Isao Kusachi, Junji Yamakawa and Masao Shirakami

Journal of Mineralogical and Petrological Sciences, Vol. 99, pp67-71 (2004)

Junji Yamakawa, Yumi Ando, Yasuhito Osanai and Isao Kusachi

Polar Geoscience, No. 14, 139--156, (2001)

The crystal Structure of scapolite from the Lutzow-Holm Bay region, East Antarctica with cell formular (Na1.97Ca1.48K0.46Mg0.03)3.94(Al4.15Si7.85Fe0.01)12.01O24.00(Cl0.65(CO3)0.42)1.07, Me39, was determined in tetragonal, P42/n, a=12.122(2); c=7.585(2) A by the single crystal X-ray diffraction method. The structure is the same as that of meionite but with some difference in atomic coordinates and Al percentage in the tetrahedron. The CO3 groups were mainly disorderd on the xy plane and off-centred from the Anion site. The cation site was 8-coordinate rather than 6-coordinate.

Baghdadite from Fuka, Okayama Prefecture, Japan

Kanako Shiraga, Isao Kusachi, Shoichi Kobayashi and Junji Yamakawa

Journal of Mineralogical and Petrological Sciences, Vol.96, page 43--47, (2001)

Baghdadite was found in a spurrite zone in skarns at Fuka, Okayama Prefecture, Japan. It occurs as anhedral grains up to 0.5 mm in length and prismatic crystals up to 0.6x0.4x0.2 mm, in association with gehlenite, spurrite, tilleyite, perovskite, grandite garnet and vesuvianite.

Kinoite from Fuka, Okayama Prefecture, Japan

Isao Kusachi, Makoto Nishimura, Kanako Shiraga, Shoichi Kobayashi, Junji Yamakawa

Journal of Mineralogical and Petrological Sciences, Vol.96, page 29--33, (2001)

Kinoite was found in a dump at the Fuka mine, Okayama Prefecture, Japan. It occures as aggregates of flakey crystals, and rarely as subhedral platy crystals up to 1 mm wide in a vein cutting into crystalline limestone. Associated minerals are stringhamaite, calsite and an unidentified mineral. The empirical formula of the mineral is (Ca2.00Mg0.02)s2.02(Cu1.92Fe0.04Co0.04)s2.00Si2.98O10, 2.25H2O on the basis of O=10 (anhydrous). The unit cell parameters are a=6.989(1), b=12.904(2), c=5.659(1) A, and beta=96.15(2) deg. The mineral is optuically biaxial negative with refractive indices alpha=1.642(2), beta=1.662(2) and gamma=1.675(2). The Vickers microhardness is 536 kg mm-2 (50 g load) and the density is 3.14 g cm-3. It is likely that kinoite at the Fuka mine was formed as a primary mineral by a reaction of Cu- and Si-bearing fluids with limestone.

Uralborite from Fuka, Okayama Prefecture, Japan

Isao Kusachi, Kanako Shiraga, Shoichi Kobayashi, Junji Yamakawa and Yasushi Takechi

Journal of Mineralogical and Petrological Sciences, Vol.95, page 43--47, (2000)

Uralborite, CaB2O2(OH)4, was found in a vein consisting of borate minerals that cut into crystalline limestone at Fuka, Okayama Prefecture, Japan. It occures as aggregates of fibrous crystals up to 0.2 mm long and as euhedral crystals up to 7 mm long and 3 mm wide, in association with sibirskite, borcarite, fluorite and calcite.

Electron microproibe analyses and ICP gave the empirical formula Ca1.006B2.069(OH)3.931 on the basis of O=6. X-ray powder diffraction were indexed on the monoclinic cell, a=6.923(1), b=12.326(1), c=9.831(1) A, \beta=97.09(1) deg, determined by a single crystal method. The mineral was optically biaxial positive with refractive indices \alpha=1.605(2), \beta=1.611(2), \gamma=1.618(2). The Vickers microhardnesss was 372 kg mm-2 and the Moh's scale of hardness was 4.5. The density was 2.58(2) g cm-1. It is likely that uralborite at Fuka was formed as a secondary mineral by a late-hydrothermal alteration of sibirskite.

Hexahydroborite from Fuka, Okayama Prefecture, Japan

Isao Kusachi, Yasushi Takeuchi, Shoichi Kobayashi, Junji Yamakawa, Yoshihiro Nakamura, Kyue-Hyung Lee and Shoji Motomizu

Mineralogical Journal, Vol. 21, No.1, pp.9-14, (1999)

Hexahydroborite was found in a vein consisting of borate minerals which developed along the boundary between crystalline limestone and skarns at Fuka, Okayama Prefecture, Japan. Hexahydroborite occurred as aggregates of pyramidal crystals up to 2 mm wide on the cavity wall, ihn association with olshanskyte and calcite. Wet analyses and ICP-MS gabe the empirical formula Ca1.001B2.102O5.846H2O on the basis of O=10, which was consistent with the ideal formula Ca[B(OH)4]2 2H2O. The reflections of X-ray powder data for hexahydroborite from Fuka were indexed on the monoclinic cell, a=16.011(2), B=6.688(1), c=7.954(2) A, \beta=103.81(1) degrees, determined by single crystal method. The mineral was optically biaxial positive with refractive indices \alpha=1.502(2), \beta=1.505(2), \gamma=1.509(2) and had a Mohs hardness of 2.5 and a density of 1.84 gcm-3. It is likely that hexahydroborite at Fuka was formed by a reaction of ground water with sibirskite and/or parasibirskite at a low temperature around 25 C.

Syntheses and X-ray studies of kimzeyite, Ca3Zr2(Al,Fe)2SiO12

Junji Yamakawa, Chiyoko Henmi and Akira Kawahara

Mineralogical Journal, Vol. 16, No.7, pp.371-377, (1993)

Kimzeyite solid solution series (Ca3Zr2Al2SiO12-Ca3Zr2Fe2SiO12) abbreviated to Al100Fe0-Al0Fe100 have been investigated by hydrothermal syntheses and X-ray powder diffraction. The latter confirmed the splitting or broadening of the diffraction peaks on the specimens with the initial composition Al50Fe50 and quenched from the temperature below 650 C. The electron microprobe analyses were also carried out and indicated the existence of two kinds of crystal grains of kimzeyite, each having a different composition. The cell dimensions calculated from the peaks of X-ray powder diffraction concluded that the splitting or broadening of these peaks in ascribed to the existence of two exolved garnet phases both having a cubic symmetry. The existence of an exolution region below 650 C in kimzeyite solid solution series has been confirmed.

Rietveld analyses of minerals

Computer simulations of chemical and physical properties of minerals