MINERALOGICAL JOURNAL, VOL . 5, No. 5, PP. 309-320, SEPT., 1968
MINERALOGICAL NOTES ON MESOLITE AND SCOLECITE FROM JAPAN
KAZuo HARADA
Section of Geology, Chichibu Museum of Natural History , Nagatoro 1417, Chichibu-gun, Saitama
MAMORU HARA
Geological and Mineralogical Institute, Faculty of Science, Tokyo University of Education, Otsuka, Tokyo
and
KAZUSO NAKAO
Chemical Institute, Faculty of Science, Tokyo University of Education, Otsuka, Tokyo
ABSTRACT
Occurrence of mesolites and scolecite was confirmed in veinlets or amyg dales in andesitic or basaltic rocks in Japan. The results of chemical, physical and X-ray studies of these minerals are described, with their mineral associ ations and modes of occurrences.
Introduction
Mesolite and scolecite are usually classified as common fibrous zeolites, but there has been no report on the occurrence of these zeolites in Japan though the thermal and chemical data of mesolite from Tezuka, Nagano, Japan, was given by Koizumi (1953). However, our routine examinations of fibrous zeolites in the National Science Museum, Tokyo, recently confirmed that mesolite and scolecite are not so rare in Japan as hitherto believed. This paper deals with the 310 Mineralogical Notes on Mesolite and Scolecite from Japan descriptions of scolecite and mesolites from Japan. a) Mesolite from Tezuka, Nishisioda-mura, Chiisagata-gun, Naga no, Japan (coll. by Takaharu Imayoshi). This mineral occurs as fibrous aggregates, sometimes associated with heulandite, in the vein lets (2-3cm wide) in andesitic tuff breccia. The DTA, TGA and chemical analysis of this specimen were provided by Koizumi (1953). b) Mesolite from Oshima, Otsuki City, Yamanashi, Japan (coll. by the writers). This mineral occurs as fibrous aggregates closely associated with stilbite in amygdales (1-2cm) of thoroughly altered olivine basalt. c) Mesolite from Waniguchi, Itoigawa City, Niigata, Japan (coll. by Takaharu Imayoshi). This mineral occurs as silky fibrous spher ules (2-3cm) in the geodes of basalt soil. Some specimens show a hair-like crystal form. d) Scolecite from Hudakake, Kiyokawa-mura, Aiko-gun, Kana gawa, Japan (coll. by Yasue Oki). This mineral occurs as veinlets (1cm wide) in andesitic tuff breccia.
Zeolite assemblages Under the polarizing microscope, some mesolites are found to contain scolecite. The Tezuka material contains about 5%, in volume of scolecite fiber. A zonal texture is apparent in the amygdales of the Oshima material; almost pure mesolite in the core of an amygdale is surrounded by the assemblage of mesolite and scolecite, and the latter is encircled by stilbite (Fig. 1). Scolecite from Hudakake often shows inter penetration-twins on {110} in the section perpendicular to the c-axis (Fig. 2). The Waniguchi and Hudakake specimens are almost pure, but detailed observations at high magnifications revealed a very small amount of thomsonite along the margins of the veinlets. Absence of quartz in all these specimens suggests that they have probably been crystallized at a low silica activity and under a non equilibrium condition. Physical data of those zeolites are shown in K. HARADA, M. HARA and K . NAKAO 311
Fig. 1. Microphotographs of mesolite, scolecite and stilbite from Oshima. A) Zoning of almost pure mesolite (M), scolecite+mesolite (SCM), and stilbite (ST), from core to rim, in an amygdale of olivine basalt (Parallel nicols). B) Aggregates of scolecite (SC) and mesolite (M) with Stilbite (ST). Stilbite (ST) is parallel to the wall of the amygdale (Parallel nicols). C) Aggregates of Scolecite (SC) and mesolite . (M) (Crossed nicols). Mesolite shows extremely low birefringence. Note: Scales represent 0.5mm in length. 312 Mineralogical Notes on Mesolite and Scolecite. from Japan
Fig. 2. Microphotographs of scolecite from Hudakake. A) (001) section. Interpenetration-twins across (110) are recognized (Crossed nicols). B) Section parallel to the c-axis. Compact mass, Chalk like variety (1) and silky fiber (2) were chemically analysed (Crossed nicols). Note: Scales represent 0.5mm in length.
Table 1. In some specimens 2V was not measured due to the very thin fibrous nature.
Chemical data
Pure specimens separated by hand-picking were analysed by the normal wet method. Mesolites from Oshima and Tezuka contained scolecite, in 5 or 10% in volume, as impurity owing to the difficulty in separation. Chemical data are shown in Table 1 together with Table 1. Chemical and physical data of mesolite, scolecite and stilbite.
Notes: 1. Mesolite from Tezuka containing about 5%, in volume, of scolecite as impurity (Analyst, K. Nakao).
2. Mesolite from Oshima containing about 10%, in volume, of scolecite (a=1 .512, ƒÀ=1.517, ƒÁ =1.518, ƒÁ-ƒ¿=0.006andc•ÈX=19 .5•‹) as impurity (Analyst, M. Hara). 3. Silky fibrous (ƒ¿) and compact massive (b) scolecite (pure material) from Hudakake
(Analysts, M. Hara (ƒ¿) and K. Nakao (b)). 4. Sodium-rich mesolite from Waniguchi (pure material) , Niigata Prefecture ((ƒ¿) fibrous aggregates; analyst, K. Nakao and (b) hair-like crystal; analyst , M. Hara). 5. Stilbite from Oshima (Analyst, M. Hara).
K. HARADA, M. HARA and K. NAKAO 313 314 Mineralogical Notes on Mesolite and Scolecite from Japan other properties. In terms of structural formulae, these correspond to:
Mesolite
(Na1.567Ca2.294)3.861 (Fe+30.007Al5.856Si9.063)14.926O30•E8.548H2O
(Tezuka, Nagano; with about 5% of scolecite as impurity),
(Na1.999K0.003Ca2.318M g0.017)4.337 (Al6.355Fe+30.029Si8.735)15.119O30• 9.332H2O
(Oshima, Yamanashi; with about 10% of scolecite as impurity), and
(Na3.723Ca1.579)5.302 (A16.379Fe0.010Si8.488)14.877O30•E8.265H20
(Waniguchi, Niigata; pure material in fibrous aggregates).
Scolecite (Na0.234K0.006Ca1.952Mg0.040)2.232(A14.172Fe+30.016Si5.982)10.170O20.6.120H2O (Hudakake, Kanagawa; pure material in silky fibers) and
(Cal.581Na0.164K0.025)1.770 (A14.151Fe+30.017Si6.036)10.204O20•E6.196H2O
(Hudakake, Kanagawa; pure material, chalk like variety in
compact masses).
Stilbite
(Na0.823K0.043Ca3.991Mg0.091)4.948(Al11.823Fe+30.195Si24.715) 36.733O72•E25.387H2O
(Oshima, Yamanashi; pure material).
Chemical compositions of scolecite and mesolite are close to the data summarized and advocated by Foster (1965), but mesolite from Waniguchi contains much more Na2O and less CaO. From both X-ray and optical observations, this specimen is very pure, so that the chemical range of mesolite may extend toward the Na-rich side. The same specimen of mesolite from Tezuka analysed by Koizumi (1953) corresponds well to the writers' reexamination . Chemical composition of stilbite provides an important point. This stilbite contains much more Al2O3 and much less SiO2 than that hitherto reported and ad vocated (Cerny, 1965). This can be explained by the low silica activity prevailing during the crystallization . This stilbite is closely associated with mesolite and scolecite in the amygdales of olivine K. HARADA, M. HARA and K. NAKAO 315 basalt (Fig. 1). The multiplicity of mineralogical associations and variations seen within an amygdale or a veinlet was caused by subtle differences in the activity of cations during crystallization .
Cation-exchange capacity Cation-exchange capacities were measured by Schollenberger and Shimon's method (Schollenberger & Shimon, 1945). The method was elucidated elsewhere (Harada & Tomita, 1967) and results are as follows: Mesolite from Tezuka, Nagano, and containing about 5% of scolecite as impurity gave 54.9meq/100g and the calculated c. e. c. based on chemical analysis gave 525.8meq/100g. The specimen from Oshima, Yamanashi, and containing about 10% of scolecite as impurity gave 119.5meq/100g and the calculated c. e. c. based on chemical analysis gave 499.6meq/100g. Scolecite from Hudakake, Kanagawa, which is a pure material in silky fibers, gave 104.5meq/100g and the calculated c. e. c. based on chemical analysis gave 531.0meq/100g. The maximum amounts of cation leached from the mesolite structure are 10.9% (Tezuka) and 23.9% (Oshima), and that from the scolecite structure is 19.7% (Hudakake), which are in contrast with the case of stilbite, where almost all the cation is exchangeable. (Harada & Tomita, 1967). The difference between these two cases maybe explained by the fact that these cations in scolecite and mesolite are bound to their frameworks stronger than those in stilbite, as surmised from the crystal structure of mesolite and scolecite (Pauling, 1930; Taylor, Meek & Jackson, 1933; Taylor, 1934).
X-ray data
X-ray powder data of mesolite from Tezuka and scolecite from Hudakake were indexed with the aid of their cell dimensions and 316 Mineralogical Notes on Mesolite and Scolecite from Japan
Table 2. X-ray powder data of mesolite from Tezuka. K. HARADA, M. HARA and K. NAKAO 317
Table 3. X-ray powder data of scolecite from Hudakake.
space groups so far reported: a=56.7A, b=6.54A, c=18.44A, ƒÀ=90•‹ and C3/2-C2 for mesolite (Hey, 1933), and a=18.48A, b=18.94A, c=6.54A,
ƒÀ= 90•‹45•L and C4/8-Cc for scolecite (Wyart, 1933; Taylor, Meek &
Jackson, 1933; Hey, 1936) as listed in Table 2 and 3 respectively.
During the courses of the indexing, the cell dimensions were 318 Mineralogical Notes on Mesolite and Scolecite from Japan
refined with the use of powder data with silicon as an internal
standard. The results are: a=56.7A, b=6.53A, c=18.47A, ƒÀ=90•‹
(•}O.O1A for the cell edges) for mesolite, and a=18.48A, b=18.96A,
c=6.54A, ƒÀ=90•‹45•L(•}0.02A) for scolecite. Mesolites from other
localities showed no appreciable discrepancy.
Heat treatments of mesolite
The starting material was mesolite from Tezuka. The mesolite
was pulverized to fine powder and spread on a silica glass slide.
Heating experiments were performed at 100•Ž, 200•Ž, 300•Ž, 320•Ž
and 340•Ž respectively for one hour. X-ray examination was then
made at room temperature after each heat treatment (Fig. 3).
Subtle changes were observed until 320•Ž and the mesolite was
decomposed into an amorphous material at 340•Ž, but detailed obser
vations revealed that pairs of reflections of 4.72A (hkl, 803) and 4.62A
(hkl, 004), 4.21A (hkl, 12, 0, 2, 12, 0, 2) and 4.15A. (hkl, 513, 604), 3.23A
(hkl, 914) and 3.17A (hkl, 420), and 2.894A (hkl, 920, 15, 1, 3) and 2.886A
(hkl, 223, 915) gradually became indistinguishable with the rise of
temperature. Finally, at 320°C, these peaks became similar to those
of gonnardite. Prolonged heat treatments of the same specimen at
320°C revealed that from 1.25 to 1.75 hours, X-ray powder data of
the materials resembled that of gonnardite, and after 2 hours mesolite
had been decomposed into an amorphous material. The dehydration
characteristic of the scolecite to metascolecite was performed by Hey
(1936) at 240•Ž to 255•Ž, and the product seems to be structurally identical to gonnardite (Deer, Howie & Zussman, 1963; p. 365). The transition of mesolite to •gmetamesolite•h or a •ggonnardite-like phase•h occurs gradually.
The writers wish to express their heartfelt thanks to Professor
Toshio Sudo and Professor Kozo Nagashima of the Tokyo University of Education for leading this study. Thanks are also due to Dr. K. HARADA, M. HARA and K. NAKAO 319
Fig. 3. X-ray powder patterns of mesolite after heat treatments, together with the pattern of gonnardite from Maze, Niigata Prefecture (Shimazu and Kawakami, 1967; Harada, Iwamoto and Kihara, 1967).
Kin-ichi Sakurai, Dr. Akira Kato and Dr. Takaharu Imayoshi of the National Science Museum, Tokyo, and Dr. Yasue Oki of the Hot Spring Research Institute of Kanagawa Prefecture, for generously providing with specimens as well as helpful comments. 320 Mineralogical Notes on Mesolite and Scolecite from Japan
REFERENCES
CERNY,P. (1965). Neues. Jahr. Min. Mh., 7, 198. DEER, W. A., HOWIE,R. A. & ZUSSMAN,J. (1963). Rock-forming minerals (4), Longmans, London, 364. FOSTER,M. D. (1965). U. S. Geol. Surv. Prof. Paper, 504-D, 1. HARADA,K. & ToMITA, K. (1967). Amer. Min., 52, 1438. HARADA,K., IWAMOTO,S. & KIHARA,K. (1967). Amer. Min., 52, 1785. HEY, M. H. (1933). Min. Mag., 23, 421. HEY, M. H. (1936). Min. Mag., 24, 227. KOIZUMI,M. (1953). Min. Jour. 1, 36. PAULING,L. (1930). Proc. Nat. Acad. Sci., 16, 453. SCHOLLENBERGER,C. J. & SHIMON,R. N. (1945). Soil Sci., 59, 13. SHIMAZU,M. & KAWAKAMi,T. (1967). Sci. Rept. Niigata Univ. Ser. E. 1, 17. TAYLOR,W. H., MEEK, C. A. & JACKSON,W. W. (1933). Z. Kristallogr., 84, 373. TAYLOR,W. H. (1934). Proc. Roy. Soc. London (A), 145, 80. WYART, J. (1933). Bull. Soc. Franc. Min., 56, 81.
Manuscript received 30 March 1968.