MINERALOGICAL MAGAZINE, MARCH 1985, VOL. 49, PP. 81 85 X-ray diffraction studies of vivianite, metavivianite, and baririte T. SAMESHIMA, G. S. HENDERSON, P. M. BLACK, AND K. A. RODGERS Department of Geology, University of Auckland, Private Bag, Auckland, New Zealand ABSTRACT. Vivianite specimens from various world employing Cu-K~ with a graphite monochromator. localities yield X-ray powder patterns of two types: one All the resulting patterns were compared with those corresponds with that shown by synthetic Fea(PO4)2 - obtained from synthetic Fea(PO4)2"8H20, type 8H~O and is not readily distinguished from that of baririte, and type metavivianite. Where necessary, baririte; the second shows reflections of monoclinic silicon was used as an internal standard. A few very vivianite and triclinic metavivianite along with reflections of a bobierrite-type phase. The triclinic phase occurs as weak reflections that could be assigned to hydrated two twin-related lattices with twin plane 110 being the halloysite and/or illite were noted in some samples structural equivalent of 010 in the monoclinic phase. The of earthy (cryptocrystalline) habit and the occa- relationship of the bobierrite-type lattice to the other two sional nodular specimen. has not been established. The ternary pattern is produced by some coarse-grained vivianites on natural oxidation. Finer grained vivianites oxidise to an X-ray amorphous Results state without passing through a triclinic intermediate. Examples of the diffraction data which were KEYWORDS: X-ray diffraction, vivianite, metavivianite, obtained are given in Tables I and II, along with baririte. some published data. Synthetic Fe3(P04) 2 . 8H20 was prepared RE C E N T X-ray diffraction studies of vivianite and according to several of the recipes given in Mellor some related iron phosphate minerals suggest that (1935). X-ray reflections obtained for all samples the status of some species needs reappraisal. For correspond well with those given on ASTM Powder example, the results of Poullen (1979), Dormann Diffraction Data cards 3-0070 and 30-0662. An and Poullen (1980), and Dormann et al. (1982) annotation to 3-0070 suggests the sample was indicate that metavivianite is not a triclinic poly- synthetic while 30-0662 is data for synthetic morph of vivianite but an intermediate oxidation material. The results given in Table I, col. 5, are product of the ferrous phosphate and contains those obtained from the precipitate formed by both Fe 2+ and Fe 3+. 'I1 en rrsulte que la mrta- mixing solutions of ferrous sulphate and sodium vivianite est un minrral toujours associ6 ~t la hydrogen phosphate. vivianite' (Dormann and Poullen, 1980, p. 633). Earthy (cryptocrystalline) vivianite. As found by Further, powder diffraction examination of twenty- Henderson et al. (1984) the majority of earthy two vivianite specimens from New Zealand locali- specimens and some more coarsely crystalline ties by Henderson et al. (1984) showed that the samples gave results which correspond well with patterns of a number of samples, but not all, ASTM card 30-0662, published data of Kleber et al. contained both monoclinic vivianite and triclinic (1965) and Dobra and Duder (1976), as well as with metavivianite lines, although the presence of the calculated d-values obtained using the lattice triclinic pattern appeared to correlate more with constants given on ASTM card 30-0662 (= US mineral habit and mode of occurrence than with National Bureau of Standards Monograph 25, degree of oxidation of the specimen (cf. Dormann section 16, p. 38). It should, perhaps, be noted here and Poullen, 1980). that these constants differ from those given by Twenty-one additional specimens of vivianite Palache et al. (1951) cf. Barth (1937), and those from well-documented localities throughout the given by Fejdi et al. (1980). world have been examined by X-ray powder dif- Typical results are given in Table I, cols. 6-9. fraction, using both Co-Ks and Fe-Ka radiation Additional samples showing a typical vivianite and 114.6 mm Debye-Scherrer cameras. Some pattern include nodular vivianite, Suhana Hime- samples were further examined by diffractometry shima Island, Japan and crystalline vivianite, (~ Copyright the Mineralogical Society 82 T. SAMESHIMA ET AL. ~oo~ ~o~o ~ o ~ ~ ~ ~o ~O~N N~ ~CO O~ O ~ oo o ~d ~>- ~:~ .~, , co ds gddM d ~ d M M MM M M M MM s163 o ~ ~-'~ > mk@@~ ~o m ~ ~N NN NNNN NN NNQ s.. d ~MMM ~ ~ M~ ~" ,~ ~ ~," ,~ ~,~ - . cx~ c-J c,~ N e~OJ ~J o ~G t--- X-RAY STUDY OF VIVIANITE 83 Spodumene Mine, Kings Mountain, North Caro- specifically identified and may be obscured by the lina, along with numerous New Zealand specimens very strong 110 vivianite reflection. as given in Henderson et al. (1984). Samples of vivianite from Hunua, New Zealand Coarsely crystalline 'vivianite'. Many X-ray dif- (AU: 2408), Puy-de-Dome, France (Smithsonian fraction photographs of specimens, such as large Institute, Bosch Collection, B14026), and Clear- crystal fragments and groups of crystals, particu- water, Idaho (Smithsonian Institute, 87220) were larly those of granular and acicular habits, show, re-examined by X-ray diffractometry using Cu-Kct along with their monoclinic vivianite pattern, the with a graphite monochromator. Results are given presence of a number of reflections which corre- in Table II. spond well with prominent reflections of meta- The Hunua cryptocrystalline sample, col. 1, is vivianite as enumerated by Ritz et al. (1974). monomineralic vivianite. No additional reflections Examples are given in Table I, cols. 13-17 and exist in its pattern. Table II, cols. 2 and 3. The Clearwater and Puy-de-Dome samples are Further specimens that show both vivianite and altered vivianites showing additional metavivianite metavivianite patterns include nodular vivianite reflections as well as the strong diffraction line at from: Tarusaka Machi, Japan; Fujie Beach, Japan; 6.9 A. In addition the Puy-de-Dome specimen also Katada, Kobe, Japan; Tomigaoka, Nara, Japan; shows peaks at (d A) 3.98, 3.46, and 2.815 which, Oshibedani, Hyogo, Japan; Washington DC; and crystalline vivianite from: Carroll, Virginia; Wannon River, Victoria, Australia; Wheal Jane, Truro, Cornwall; and various New Zealand samples TABLE II. X-ray powder diffraction data for as given in Henderson et al. (1984). 'vivianite' samples derived using a graphite mono- Similar patterns showing both sets of reflections chromator; d (.~) 8.8-2.4 have been recorded without comment by Minato et al. (1956) and Zwann and Kortenburg van der 1 la 2 2a 3 3a Sluys (1971) from Haren, Noord Brabant Province, Netherlands (Table I, cols. 11 and 12). Presumably, 8.77 4 8.8 1 it was this type of binary pattern that Poulten (1979, 7.93 37 8.01 2 7.91 5 p. 51) obtained within his grouping 'Vivianites 6.96 100 6.92 30 naturelles oxydres artificiellement'. 6.71 100 6.76 89 6.70 100 4.955 3 In the present examples, there are generally 4.906 40 4.905 3 4.901 5 distinct metavivianite reflections close to 8.6 and 4.535 7 4.493 2 4.570 1 2.8 A. Depending on exposure times, further lines 4.353 2 4.366 1 4.353 1 may be noted at (d A) 4.27, 3.01, 2.25, and 1.63. 4.073 10 4.095 3 4.077 7 Vivianite reflections at d (A) 6.73 (020), 4.90 (200), 3.980 2 4.34 (011), 3.85 (101), 2.96 (211), 2.64 (330), 2.53 3.857 14 3.800 2 3.850 3 (141), 2.42 (301), 1.89, 1.79, 1.66, and 1.60 are 3.636 5 3.650 1 3.650 1 coincident with, or close to metavivianite lines at 3.460 2 3.356 <1 (d A) 6.72 (li0), 4.89 (110), 4.27 (0il), 3.84 (011,210), 3.202 26 3.214 7 3.209 7 3.978 40 2.985 2 2.988 4 2.95 (021), 2.67 (201), 2.50 (320), 2.46 (300), 1.86, 1.82, 2.967 3 1.75, 1.665, and 1.60. 2.815 1 A prominent reflection at 6.90-6.97 A frequently 2.768 4 2.775 3 2.771 2 occurs in those patterns showing metavivianite 2.718 19 2.714 4 2.725 4 lines and appears to show sympathetic variation in 2.700 17 2.711 5 intensity with that occurring at 8.6A. The same 2.639 10 2.640 2 reflection was recorded by Minato et al. (1956) in 2.592 2 2.600 3 2.594 3 their Ashio Mine sample (Table I, col. 12). Such a 2.524 11 2.536 2 reflection does not occur in the pattern of type 2.431 13 2.430 5 2.424 3 metavivianite nor can it be indexed using the lattice constants of Ritz et al. (1974). However, 6.96A is 1. Earthy (cryptocrystalline) vivianite; Hunua, New Zea- the strongest reflection of bobierrite as given by land. AU: 2408. Frazier et al. (1963) which is that data given on 2. Crystalline vivianite; Menat, Puy-de-dome, France. US National Museum (Karl Bosch Collection): ASTM Diffraction Data File card 16-0330. Of B14026. other strong reflections of bobierrite, those at (d A) 3. Crystalline vivianite; Dent, Clearwater Co., Idaho, 3.02 (i71), 2.94 (350), 2.57 (191), and 2.41 (291, 2, US National Museum: 87220. 10, 0) are coincident with or close to vivianite or la, 2a, 3a. Relative intensities of reflections given in metavivianite reflections; 8.04A (120) was not 1, 2, 3, respectively. 84 T. SAMESHIMA ET AL. along with that at 6.96 A, are common to bobier- sion, the term 'triclinic phase' will be used for that rite.