Yugawaralite | |Ca2 (H2O)8| [Al4Si12O32] | ||
Morphology: | |||
Tabular parallel to {010} to 8 cm; in groups of nearly parallel crystals. | |||
Physical properties: | |||
Cleavage: {401} distinct, {101} imperfect. Fracture: conchoidal. Hardness: 4.5 - 5. D = 2.20 to 2.23 gm/cm3. Luster: vitreous to pearly, iridescent on {010}. Streak: white. |
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Crystals of yugawaralite, 10 mm wide, from Kurar quarry in Bombay-Malad, India | |||
Optical properties: | |||
Color: colorless to white; colorless in thin section. Biaxial (- or +). α = 1.492 – 1.496, β = 1.497 – 1.499, γ = 1.502 - 1.504, δ = 0.005 - 0.006, 2Vx = 48° - 89°. X ˄ c = 6°-9°, Z = b. Dispersion: r < v, weak to distinct. |
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Crystallography: | |||
Unit cell data: a 9.700, b 13.972, c 10.039 Å, β 111.07°. Z = 1, Space group Pc. (Kvick et al. 1986). |
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Name: | |||
Yugawaralite was described by Sakuri and Hayashi (1952) and named for the type locality at Yugawara Hot Springs, Kanagawa Prefecture, Honshu, Japan | |||
Crystal structure: | |||
The framework topology of yugawaralite (YUG) space group C2/m is reduced to the acentric space group Pc, owing to complete (Si,Al) ordering (Kerr and Williams 1967, 1969); Leimer and Slaughter 1969; Eberlein et al. 1971; Kvick et al. 1986). The mineral is thus piezo- and pyroelectric (Eberlein et al. 1971). Symmetry reduction to P1 has been reported on the basis of optical measurements (Akizuki 1987). Four-membered rings of tetrahedra are occupied by three Si and one Al (grey and green, respectively in the accompanying figure) in an ordered fashion. The structure possesses two types of channel systems confined by eight-membered rings. One channel extends parallel to the a-axis (aperture 2.8 x 3.6 Å), and the other is parallel to the c-axis (aperture 3.1 x 5.0 Å), shown here. | |||
Ca (red) resides at the intersection of the two types of channels and is bonded to four framework oxygens and four H2O molecules. A neutron single-crystal structure refinement at 13 K (Kvick et al. 1986) located the proton positions. The dehydration of yugawaralite, including an accompanying phase transition at about 200°C, was studied by Gottardi and Galli (1985) and Alberti et al. (1994). | |||
Chemical composition: | |||
The compositions of known samples are fairly consistent, as would be expected from a zeolite with an ordered structure. The variation in Si content between 11.8 to 12.2 atoms per unit cell is probably beyond analytical error. Non-framework elements are predominantly Ca; all others are consistently minor. | |||
Occurrences: | |||
Yugawaralite is a rare zeolite occurring in altered basaltic and other volcanic rocks in areas of very high geothermal gradients, such as active hydrothermal systems.
Thermal metamorphism of sediment and sedimentary rocks More commonly yugawaralite occurs in cavities or veins cutting lavas associated with sedimentary sections that have been weakly metamorphosed. For example, yugawaralite, associated with laumontite and calcite, occurs in cavities of basaltic lavas and pillow breccia at Nukabira, Hokkaido, Japan (Konno and Aoki 1977). The lavas along sediments of the Neogene Horoka Formation have been intruded by andesite causing a very low-grade of metamorphism. Diagenesis of basalt and other kinds of lava flows Hydrothermal systems. Bargar and Beeson (1981) and Bargar et al. (1981) describe yugawaralite in core from two drill holes, Y-2 and Y‑3 in the Lower Geyser Basin, Yellowstone National Park, Wyoming. Despite the fact that the wall rocks are rhyolitic tuff, several calcic-zeolites occur in these cores. In drill hole Y-2 yugawaralite occurs in a narrow zone at a temperature of about 200°C, and in hole Y-3 it occurs where the temperature is about 270°C. The presence of yugawaralite and wairakite in the Abanico Hill area indicate an abrupt change in the burial metamorphic effects in an Upper Cretaceous and Tertiary sequence of central Chile (Vergara et al. 1993). Zoning toward a graben indicated by yugawaralite±laumonite and then wairakite±epidote is evidence for a fossil “geothermal-type” alteration overprint on the regional zeolitic burial metamorphism. The occurrence of yugawaralite along the Chena River east of Fairbanks, Alaska, is in veins cutting a siliceous xenolith (20m by 50m) in a small porphyritic quartz monzonite pluton (Eberlein et al. 1971). The host rock is a brecciated metachert, and fractures are filled or partially filled with yugawaralite associated with quartz, laumontite, stellerite, and stilbite. The occurrence of yugawaralite and laumontite suggest hydrothermal fluids may have precipitated the zeolites. Crystals of yugawaralite occur with heulandite, stilbite, and laumontite in veins of hydrothermally altered basalt at Hvalfjordur, Borgafjardarsysla north of Reykjavik, Western Iceland (Tschernich 1992). Yugawaralite occurs with laumontite, wairakite, calcite, and quartz in Jurassic basaltic rocks of the Letba Formationb (Karoo sequence) along the Mukuze Rover, northwest of Mkuze, northeastern KwaZulu-Natal, South Africa (Weinert et al. 2000). It is suggested that this assemblage formed by the thermal metamorphism associated with a local dolerite dike. |
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References: | |||
Akizuki, M. 1987. An explanation of optical variation in yugawaralite. Min. Mag. 51, 615-620.
Alberti, A., Quartieri, S., and Vezzalini, G. 1994. Structural modifications induced by dehydration in yugawaralite. In Zeolites and Related Microporous Materials. State of the Art 1994. Weitkamp, J., Karge, H.G., Pfeifer, H., and Höldrich, W. (eds) Studies in Surface Science and Catalysis 84, 637-644 Bargar, K.E. and Beeson, M.H. 1981. Hydrothermal alteration in research drill hole Y-2. Lower Geyser Basin, Yellowstone National Park, Wyoming. Am. Mineral. 66, 473-490. Bargar, K.E., Beeson, M.H. and Keith, T.E.C. 1981. Zeolites in Yellowstone National Park. Min. Rec. 12, 29-38 Barrer, R.M. and Marshall, D.J. 1965. Synthetic zeolites related to ferrierite and yugawaralite. Am. Mineral. 50, 484-489. Eberlein, G.D., Erd, R.C., Weber, F. and Beatty, L.B. 1971. New occurrence of yugawaralite from the Chena Hot Springs area, Alaska. Am. Mineral. 56, 1699-1717. Gottardi, G. and Galli, E. 1985. Natural Zeolites, Springer-Verlag, Berlin, Germany. 409 pp. Harada, K., Nagashima, K. and Sakurai, K. 1969. Chemical composition and optical properties of yugawaralite from the type area. Am. Mineral. 54, 306-309. Houghton, B.F. 1982. Low-grade metamorphism of the Takitimu Group, western Southland, New Zealand. New Zeal. J. Geol. Geophys. 25, 1-19. Kerr, I.S. and Williams, D.J. 1967. The crystal structure of yugawaralite. Z. Kristallogr. 125, 220-225. Kerr, I.S. and Williams, D.J. 1969. The crystal structure of yugawaralite. Acta Crystallogr. 25, 1183-1190. Konno, H. and Aoki, M. 1977. Yugawaralite from Nukabira, Hokkaido. Mineral. Jour. 8, 456-462. Kvick, Å., Artioli, G. and Smith, J.V. 1986. Neutron diffraction study of the zeolite yugawaralite at 13 K. Z. Kristallogr. 174, 265-281. Leimer, H.W. and Slaughter, M. 1969. The determination and refinement of the crystal structure of yugawaralite. Z. Kristallogr. 130, 88-111. Pongiluppi, D. 1977. A new occurrence of yugawaralite at Osilo, Sardinia. Can. Mineral. 15, 113-114. Sakurai, K. and Hayashi, A. 1952. “Yugawaralite”, a new zeolite. Sci. Rep., Yokohama Nat. Univ., Ser II, 1, 69-77. Sameshima, T. 1969. Yugawarlite from Shimoda, Shizuoka Prefecture, central Japan. Geoscience Journal (Journal of the Japanese Association of Amateur Mineralogists) 20, 71-78 (Mineralogical Abs. 29-77). Seki, Y., Oki, Y., Matsuda, T., Mikami, K. and Okumura, K. 1969. Metamorphism in the Tanzawa Mountains, Central Japan. J. Japan. Assoc. Miner Petrol. Econ. Geol., 61, 1-75. Seki, Y. and Okumura, K. 1968. Yugawaralite from Onikobe active geothermal area, northeast Japan. Jour. Japan. Assoc. Min. Petr. Econ. Geol., 60, 27-33. Tanaka, T., Kimura, R., Akizuki, M. and Kudoh, Y. 2002. Origin of low-symmetry growth sectors in edingtonite and yugawarlite, and the crystal structure of the k{011} and v{120} sectors of yugawaralite. Min. Mag. 66, 409-420. Tschernich, R.W. 1992. Zeolites of the World. Geoscience Press, Tucson, Arizona. 563 pp. Vergara, M., Levi, B. and Villarroel, R. 1993. Geothermal-type alteration in a burial metamorphosed volcanic pile, central Chile. J. Metam. Geol. 11, 449-454. Weinert, C.H., Weinert, S.W. and Dunlevey, J.N. 2000. Yugawaralite in the Letaba formation, northeastern KwaZulu-Natal, South Africa. South African J. Geol. 103, 69-73. Wise, W.S. 1978. Yugawaralite from Bombay, India. Min. Rec. 9, 296. |