J. Japan. Assoc. Min. Petr. Econ. Geol., 71, 183-192, 1976

A NEW COPPER SULFATE-CARBONATE HYDROXIDE HYDRATE MINERAL, (Mn, Ni, Cu)8(SO4)4(CO3)(OH)6¥48H2O, FROM NAKAURI, AICHI PREFECTURE , JAPAN

JUJIN SUZUKI Department of Earth Sciences, Aichi University of Education, Kariya

MASAHIRO ITO

Laboratory of Earth Sciences, Department of General Education , Nagoya University, Nagoya

TSUTOMU SUGIURA

Department of Chemistry, Aichi University of Education , Kariya

Nakauriite is a new mineral found as fissure-fillings in serpentinite . There are two types appearing in different modes of occurrences, and showing a few faint differences in X-ray diffraction and DTA patterns. Both show very fine needle-like and prismatic forms with characteristic sky-blue color. It is effervescent in HC1, H,S04 and HNO3. Chemical

analysis gave Mn0 .01, N10.231 Cu7.770 (SO4)3.904(CO2) (OH)6.232 48.4H2O or (Mn, Ni, Cu)8 (SO4)4 (CO3) (OH)6.48H2O as C=1 for empirical cell contents. The most intense X-ray diffraction lines (in A) are 7.31 (100), 4.840 (14), 3.936 (14), 3.652 (20), 3.552 (13), 2.397 (14), 2.367 (16), 2.332 (14) and 1.9148 (16). The 7.823A-line appears with variable intensities. Nakauriite is pleochroic, X-colorless, Y=very light greenish blue, Z=pale sky-blue to very light blue. The mineral is biaxial negative with ƒ¿=1.585, ƒÀ=1.604, ƒÁ=1.612 (all•}0.001), 2V(-)=65.3

(calc.), showing positive elongation. Extinction is parallel to the outline. Five endothermic reactions are found at 78, 150, 186, 330 and 396•Ž of peak maxima, respectively, the last two being characteristically strong. Infrared absorption gives two characteristic bands at 3000 and 1360cm-1. The name is for the locality.

INTRODUCTION on New Minerals and Mineral Names, IMA. At first, this very clear sky-blue mineral Many species of ore minerals have been was found on some serpentinite fragments known in the serpentinite mass, that is, removed from an abandoned mine in Sam magnetite, native copper, chalcocite, cup bagawa metamorphic belt at Nakauri, about rite, digenite, djurleite, cobalt pentlandite, 6km southeast of Shinshiro, Aichi Pre heazlewoodite, and as secondary minerals, fecture, Japan. Soon after, this mineral was tenorite, malachite, brochantite and azurite. noted to occur as fracture-fillings in the Only two sulfate-carbonate hydroxide brucite-bearing serpentinite mass and was hydrate minerals have been reported so far: named nakauriite for the locality. The carbonate-cyanotrichite (Ankinovich et al., mineral and the name were approved in 1963) and jouravskite (Graudefroy and advance of publication by the Commission Permingeat, 1965). Nakauriite is the third

(Manuscript recieved, April, 2, 1976) 184 J. Suzuki, M. Ito and T. Sugiura one of this kind. In this paper, detailed description of this mineral will be reported in comparison with that of carbonate cyanotrichite which is somewhat similar to nakauriite in appearance.

MODE OF OCCURRENCE Nakauriite which is conspicuously sky blue in color by the naked-eye is found as fissure-fillings in the fractured serpentinite body containing hard and massive Fig. 1. A mode of occurrence of nakauriite. serpentinite blocks. The serpentinite is composed mainly of serpentine minerals, in X-ray diffraction and DTA patterns, opaque minerals, brucite, pyroaurite, which will be discussed in each section artinite, hydromagnesite, "yoshikawaite"1) mentioned below. (Suzuki and Ito, 1973), coalingite and aragonite. Coalingite occurs as veins as OPTICAL AND OTHER PHYSICAL PRO sociated with pyroaurite. PERTIES Nakauriite shows two modes of occur Nakauriite occurs commonly as bundled rences: Type 1 and Type 2. aggregates of very small slender to fibrous Type 1 occurs as veins cutting the crystals, whose sizes are less than about 0.2 massive serpentinite and the fractured mm in length, 0.006mm in width. It is serpentinite. The mineral is commonly clear sky-blue in color and pleochroic with associated with chrysotile and a small X=colorless, Y=very light greenish blue, amount of magnetite, and rarely with broch Z=pale sky-blue to very light blue. The antite and malachite in massive serpentinite. refractive indices for sodium light are ƒ¿= Type 2 occurs along fractures in sheared 1.585•}0.001, ƒÀ=1.604•}0.001, ƒÁ=1.612 serpentinite. It is commonly associated •} 0.001 by the immersion method. Birefring with chrysotile, magnetite, artinite and ence is moderate; ƒÁ-ƒ¿=0.027, ƒÀ-ƒ¿=0.019, pyroaurite. Free growth of very fineƒÁ-ƒÀ =0.009. The minera is biaxial nega grained slender crystal aggregates of the tive with 2V(-) 65.3•K(calculated). Extinc mineral is commonly found in the small tion is parallel to the outline of the crystal openings of fractured serpentinite (Fig. 1.). with positive elongation. Cleavage and Crystals of Type 2 are relatively smaller twinning are not observed. than those of Type 1, commonly associated The density was determined by flota with fair amounts of extremely fibrous ones. tion of clear crystals in Clerici solution, Any distinguishable differences in which gave a value of 2.39•}0.02g/cm3. chemical composition and optical properties The denity calculated by Gradstone and are not observed between the two types. Dale's equation is 2.30g/cm3, in well agree However, some slight differences are noticed ment with the observed value.

1) Application to the IMA Commission on New Minerals and Mineral Names for an approval of the name is pending. A new copper sulfate-carbonate hydroxide . hydrate mineral 185

Carbonate-cyanotrichite shows similar ponent in nakauriite. Although the sample pleochroism, but has higher refractive was prepared by careful hand-picking under indices and double refraction, showing the binocular microscope, even the most optically positive sign and negative elonga purified concentrate was still found to be tion. contaminated by chrysotile, judged from the data of DTA. CHEMICALCOMPOSITION Quantitative chemical analysis for the The sample which was thoroughly purified sample was made by atomic absorp tion analysis for CaO, MgO, total iron, MnO purified was used for qualitative analysis by X-ray fluorescence method. Electron and CuO, flame spectrochemical analysis for Na2O and K2O, titration method for Fe2O3, probe microanalysiswas also made in order to check the validity of the data obtained by the X-ray fluorescenceanalysis. As the Table 2. X-ray powder diffraction data for na kauriite from Nakauri, AichiPrefecture, specimen is too brittle to prepare evenly Japan. polished section for EPMA, hand-picked specimen mounted on extremely pure bery llium plate was carbon-coated as it was. Effervescency in HCl, H2SO4 and HNO3 positively shows the presence of CO,-com

Table 1. Chemical compositions of nakauriite and associated chrysotile from Nakauri, Achi Prefecture, Japan.

A. Nakauriite and the admixed chrysotile. * Plus serpentine mineral . B. Chrysotile associated with nakauriite. ** For not-pulverized slender crystals. C. Nakauriite, corrected for the admixed 1) Calculated by A. Kato. Orthorhombic, a 14.585, chrysotile and normalized. b 11.47, c 16.22A, Z=2, density (calc) 2.35g/cm3. 186 J. Suzuki, M. Ito and T. Sugiura gravimetric analysis for A12O3, SiO2 and and 1:1, respectively. H2O, spectrophotometric analysis for TiO2 and SO42-,and volumetric analysis for CO2. X-RAY DATA The chemical composition of the purified sample and the chrysotile associated with X-ray powder data for the new mineral nakauriite are listed in Table 1, together were obtained, using Ni-filtered CuKa radia with the rationalized mole percentages. tion. The whole X-ray diffraction data at Contamination effect by the admixed chry room temperature are shown in Table 2 and sotile was eliminated based on the SiO2 Figure 2. Nakauriite gives clearly different content of the purified sample. pattern from that for carbonate-cyanotri The formula of nakauriite is Mn0.019 chite. Ni0.231Cu7.770(SO4) 3.904 (CO3) (OH)6.232 ¥48.4H2O, Some differencesare noted in the X-ray and is idealized as (Mn, Ni, Cu)8 (SO4)4(CO3) diffraction patterns of Type 1 and Type 2 (OH)6¥48H2O as C =1 for empirical cell of nakauriite as follows: (1) The reflection contents. Although a very small amount line of 7.82A appears characteristicallyin of ZnO and Fe2O3are found in the chemical Type 2, and shows change of peak height analysis, these may be neglected for the depending on the orientations; if the chemical formula of the mineral. The mole powder specimen is rubbed strongly on ratio of SO4 to CO3 of nakauriite, carbonate the holder, the peak height increases. Type cyanotrichite and jouravskite is 4:1, 1:2 1 shows fairly faint reflectionline of 7.82A,

Fig. 2. X-ray diffraction patterns for nakauriite, A, Type 1; B , Type 2. CuK. radiation was used for 2Į. A new copper sulfate-carbonate hydroxide hydrate mineral 187

even undetectable in some cases. But it not changed by orientation effect mentioned appears distinguishable when the sample is above. rubbed strongly on the holder (3) The whole reflection lines for Type 2 .(2) The patterns for the reflection lines of are generally weaker than those for Type 1. medium peak heights are characteristically The reflection lines of 7.31 and 3.65A different between the two types especially in may be assigned to those of the admixed the range of d-spacing of 5.54 to 3.43A and chrysotile. But these lines are concluded to 2.43 to 2.31A. Apparent peak heights of be essential ones for nakauriite, based on lines of 3.55 and 1.914A are also distinctly their thermal behaviours. The thermal different on the patterns between the two effects on the whole X-ray diffraction pat types. These relations in peak heights are terns of the mineral were investigated by

Fig. 3. X-ray diffraction patterns for thermal decomposition products of nakauriite at various temperatures. A, Type 1; B, Type 2. CuKƒ¿ radiation was used for 2ƒÆ. 188 J. Suzuki, M. Ito and T. Sugiura

the high temperature X-ray diffraction THERMAL DATA apparatus. The samples were heated in air Simultaneous DTA-TG curves of naka up to various temperatures at the rate of uriite are shown in Figure 4. The heating 20•Ž per minute and held at the tem rate is 20•Ž per minute. Two strong

peratures through X-ray diffraction measu endotherms with maxima at 330 and 396•Ž rements. Outline of the thermal effects is are found, together with the three weak ones shown in Figure 3. The thermal behaviour at 78, 150 and 186•Ž. The latter three above 250•Ž is practically the same between endotherms are distinctly found for Type 2, the two types. The reflection lines of 2.40 but for Type 1 they are very faint. and 2.61A of Type 1 begin to be broadened The weight loss up to 240•Ž is estimated at 180 and 190•Ž, respectively. Other lines to be 2.8% (mean) for Type 1 and 3.3% decrease gradually the peak heights with (mean) for Type 2, on the TG curves, follow rising temperature. At 400•Ž a decomposi ed by correction for the admixed chrysotile tion phase is already formed showing some and for the apparent mass-gain due to broad lines of 4.82, 3.66, 2.53, 2.29, 2.12 and furnace air turbulence. The DTA patterns 1.498A. The pattern obtained at 1000•Ž in the higher temperature region are is neither tenorite nor cuprite. Such

thermal changes of Type 1 just mentioned

above are observed at comparatively higher

temperatures than those of Type 2.

Thermal behaviour below 300•Ž of Type

2 of nakauriite is to be noted. The 7.82A

- line begins to decrease gradually its peak

height and d-spacing with rising tem

perature above 90•Ž, and is hidden by the strong 7.31A-line at 140•Ž. Broadening

of 2.40 and 2.61A lines begins already

at 90 and 140•Ž, respectively. A new broad

line of 6.3A appears at 200•Ž, decreasing

its d-spacing gradually with rising tem

perature to 6.03A, at 280•Ž. At 400•Ž a

perfectly new diffraction pattern for a decomposed phase appears, which is the

same as that of Type 1.

The 7.8A-line reappears when the

specimen heated below 240•Ž is cooled

down to the room temperature, whose peak

height is a half of the unheated one. This is

probably due to the adsorption of water and

possibly CO2 in air. Fig. 4. Simultaneous DTA-TG patterns of na kauriite in air at atmospheric pressure. A, Type 1; B, Type 2. S=Admixed chry stoile. Heating rate is 20•Ž/min. A new copper sulfate-carbonate hydroxide hydrate mineral 189 characteristically simple, showing only two riite is clearly seen by the scanning electron strong endotherms, in contrast to that microscopic photograph as shown in Figure carbonate-cyanotrichite and jouravskite 5a. The electron diffraction pattern is show fairly complex patterns. It should be shown in Figure 5b, suggesting an orthor stressed that such a simple pattern of naka hombic lattice, which may be caused by uriite may suggest some informations on the heat effect due to electron beam. Figure 5c bonding states of gaseous components in and 5d show electron microphotographs of the crystal structure. the mineral with admixed serpentine mineral and the diffraction pattern of the latter mineral, respectively. Nakauriite is found ELECTRON MICROSCOPIC DATA as short lath-like crystals and the admixed Long prismatic morphology of nakau serpentine mineral very long fiber and platy

Fig. 5 a. Scanning electron microphotograph of nakauriite. 5 b. Electron diffraction pattern of nakauriite. Heat effect due to electron beam may be considered. 5 c. Electron microphotograph of nakauriite with admixed serpentine mineral. 5 d. Electron diffraction fiber photograph of chrysotile found in Figure 5c. 190 J. Suzuki, M. Ito and T, Sugiura

crystals. The diffraction photograph of the Table 3. Infrared absorption data (in cm-1) for very long fibrous serpentine mineral shows nakauriite and associated serpentine mineral from Nakauri, Aichi Prefecture, the flared spots characteristically found in Japan. the diffraction pattern of chrysotile. The platy one is probably lizardite, a small amount of which is detected in the X-ray powder pattern.

INFRARED SPECTRA

Infrared absorption spectra of naka uriite and the associated serpentine mineral were obtained by the KBr disc technique as shown in Figure 6. The frequencies of bands are also shown in Table 3. Some absorption bands are probably A. Nakauriite (Type 1) with the admixed serpen tine mineral. B. Nakauriite (Type 2) with the admixed serpen tine mineral. C. Associated serpentine mineral. s, strong; m, medium; w, weak; vw, very weak; sp, sharp; b, broad; vb, very broad; sh, shoulder; plat, plateau.

caused by the admixed serpentine mineral, as even the very carefully separated speci mens of nakauriite always contain fair amounts of serpentine mineral. In 2000 to 4000cm-1 region, two sharp and very strong bands are considered to be from the mineral and the admixed serpentine mineral, and the band around 3000cm-1 is assigned to the mineral. Some differences in in tensity of the absorption bands between the two types in this region may be expl ained by the amounts of admixed serpentine mineral. In 800 to 2000cm-1 region, a broad and strong band of 1360 to 1355cm-1 associated with a shoulder of 1405cm-1 is characteristically observed, and assigned Fig. 6. Infrared absorption spectra of nakauriite to the mineral. A few bands in 900 to and associated serpentine mineral. A, 1100cm-1 region may be assigned to the Type 1; B, Type 2 (all contain some amounts of serpentine mineral) ; C, ser admixed serpentine mineral. In 400 to pentine mineral. 800cm-1 region, two strong . bands are A new copper sulfate-carbonate hydroxide hydrate mineral 191

found in the pattern, which may be also terns of the two types of the mineral ? Two caused by the admixed one. interpretations may be possible . It is important to note that any 1) The two types of the mineral are

distinct differences are not found between essentially not different. The observed

the spectra of the two types of nakauriite . slight differences are due to a small amount

of water not affecting the crystal structure. DISCUSSIONS A few reasons to support this explanation are as follows: (a) The 7.82 A-line is also Some differences are found in X-ray essential for Type 1, because this appears diffraction and DTA patterns of the two in Type I when the sample is well oriented types of nakauriite, which are classified in the holder. (b) The difference on the from the modes of occurrences. DTA patterns below 300•Ž between the two The reflection lines of 7.82, 3.93, 2.61A types is not essential, because Type 1 also and so on observed in the X-ray diffraction shows the same though faintly, endotherms.

pattern of Type 2 may be assigned to those 2) There are originally two types of of pyroaurite commonly occurring in ser nakauriite. The differences observed on

pentinite. Judging from the peak heights the X-ray diffraction and DTA patterns relation of pyroaurite, most of these lines between the two types are due to the dif will overlap the pattern of Type 1. Ther ferent degree of mixing of the two. Some mal behaviour of pyroaurite was also in samples separeted as Type 2 may be vestigated in order to solve this problem. admixed by various amounts of Type 1. Thermal change of pyroaurite begins Judging from the X-ray diffraction pattern, clearly at lower temperature by 30•Ž than Type 1 will be comparatively less admixed that of Type 2. Pyroaurite decreases the with Type 2. However, it is impossible to spacing of 7.82A to 7.75A at 80•Ž and to discriminate strictly between these two 7.61 A at 120•Ž. By 140•Ž, this line is types even under microscope, though Type 2 overlapped on 7.31 A-line of the admixed of nakauriite occurs in more fibrous form serpentine mineral. During the thermal than Type 1. change of this line, a new broad reflection In any case, it is very important to line of 6.46A appears distinctly, decreasing note that some n-order reflection lines of its d-spacing of 6.2A at 270•Ž. The 7.8 7.82A are distinctly found on the diffrac A-line of pyroaurite is also rapidly revived tion pattern of Type 1, too, and that the from the 270•Ž heated sample after about infrared patterns are practically the same only ten minutes of cooling at room tem in respect to each other. Judging from these

perature. Judging from these facts, it facts, the crystal structures of the two types may be concluded that the thermal be are conjectured to be actually the same. haviour of Type 2 of nakauriite up to 300•Ž Some features characteristically observed is similar to but is not identical with that for Type 2 might be caused by the electron of pyroaruite, and that the 7.8 A-line of microscopically fibrous form and possibly nakauriite is not caused by the admixed small amount of loosely bounded water not

pyroaurite but is essential for nakauriite. affecting the crystal structure. If so, why are some differences observed in the X-ray diffraction and the DTA pat 192 J. Suzuki, M. Ito and T. Sugiura

ACKNOWLEDGMENTS analysis, respectively.

Sincere thanks are due to Dr. K. Saku rai and Dr. A. Kato of National Science REFERENCES Museum, Prof. M. Nambu of Tohoku Univer Ankinovich, E. A., Gekht, I. I. and Zaitseva, R. sity, and Dr. Y. Tsuzuki of Nagoya Univer I. (1963), A new variety of cyanotrichite carbonate-cyanotrichite. Zapiski Vses. sity for much helpful suggestions and dis Mineralog. Obshch., 92, 458-463. (in cussions. We are also indebted to Dr. I. Russian) Nishida of Nagoya University for kindly Graudefroy, C. and Permingeat, F. (1965), La jouravslcite, une nouvelle espece minerale. providing some of electron microphoto Bull. Soc. franc. Mindr. Crist., 88, 254-262. graphs and Dr. H. Nakata of Aichi Univer Suzuki, J. and Ito, M. (1973), A new magnesium sity of Education and Mr. Y. Yusa of carbonate hydrate mineral, Mg5(CO3)4 (OH)2¥8H2O, from Yoshikawa, Aichi Pre Nagoya University for kindly assisting in fecture, Japan. Jour. Japan. Assoc. Min. infrared spectra analysis and microprobe Pet. Econ. Geol., 68, 353-361.

愛 知 県 中 宇 利 産 含Ni, Cu-SO4-CO3-OH-H2O鉱 物 の 一 つ,中 宇 利 石 に つ い て .

鈴 木 重 人,伊 藤 正 裕,杉 浦 孜

本 鉱 物 は,三 波 川 帯 中 の 各種 銅 鉱 物 を と もな う蛇紋 岩 体 の 割 れ 目 よ り発見 され た 。 細 か な 針 状 な い し 長柱 状 をな し,特 徴 的 なsky-blueの 色 を呈 す る。 構造 式(C=1)と して. Mn0.018Ni0.231 Cu7.770 (SO4)3.804(CO3) (OH)6.232 ¥48.4H2O

ま た は, (Mn, Ni, Cu)8(SO4)4(CO3)(OH)6・48 H2Oを も つ 。

本 鉱 物 の 光 学 的 性 質, X線 回 折,電 子 線 回 折, DTA-TG, IR.パ タ ー ン に 見 ら れ る諸 性 質 に つ い て 報 告 し た 。 ま た,産 状 の 違 い に よ り, X線 回 折 お よ びDTAパ タ ー ン に 僅 か な 違 い が 見 ら れ,こ れ ら に つ い て も 検 討 し た 。 Nakauri, Shinshira, Aichi Prefecture愛 知 県 新 城 市 中 宇 利