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Frost, Ray L. and Keeffe, Eloise C. and Reddy, B. Jagannadha (2010) Characterisation of Ni carbonate-bearing minerals by UV-Vis-NIR spectroscopy. Transition Metal Chemistry, 35(3). pp. 279-287.
© Copyright 2010 Springer Verlag
1
Characterisation of Ni carbonate-bearing minerals by UV-Vis-NIR spectroscopy 1
2
B. Jagannadha Reddy, Eloise C. Keeffe and Ray L. Frost 3
4
Inorganic Materials Research program, School of Physical and Chemical Sciences, 5
Queensland University of Technology, GPO Box 2434, Brisbane Queensland 4001, 6
Australia. 7
Abstract 8
9
Four nickel carbonate-bearing minerals from Australia have been investigated 10
to study the effect of Ni for Mg substitution. The spectra of nullaginite, zaratite, 11
widgiemoolthalite and takovite show three main features in the range 26720-25855 12
cm-1(1-band), 15230-14740 cm-1(2-band) and 9200-9145 cm-1(3-band) which are 13
characteristic of divalent nickel ion in six-fold coordination. Crystal Field 14
Stabilization Energy (CFSE) of Ni2+ in the four carbonates is calculated from the 15
observed 3A2g(3F) 3T2g(
3F) transition. CFSE is dependent on mineralogy 16
crystallinity and chemical composition (Al/Mg-content). The splitting of 1-band and 17
3-band and non-Gaussian shape of 3-band in the minerals are the effects of Ni-site 18
distortion from regular octahedron. The effect of structural cation substitutions (Mg2+, 19
Ni2+, Fe2+ and trivalent cations, Al3+, Fe3) in the carbonate minerals is noticed on 20
band shifts. Electronic bands in the UV-Vis-NIR spectra and the overtones and 21
combination bands of OH and carbonate ion in NIR show shift to higher 22
wavenumbers and shift is more significant in the case of widgiemoolthalite and 23
takovite. 24
25
26
Keywords: Inorganic compounds; Near-infrared spectroscopy; Crystal fields; Optical 27
properties 28
29
30
31
32 Author for correspondence ([email protected])
2
1. Introduction 33
34
Nullaginite Ni2(CO3)(OH)2 and zaratite Ni3(CO3)(OH)4.4H2O are the two 35
hydroxy nickel carbonate minerals. Nullaginite belongs to rosasite group [1-8] and is 36
found to form in the oxidised zone of nickel rich hydrothermal ore deposits. Zaratite 37
is of an unknown structure and is an uncommon secondary mineral formed by 38
alteration of chromite, pentlandite, pyrrhotite and millerite in ultramafic rocks. 39
Widgiemoolthalite (Ni,Mg)5(CO3)4(OH)2.4-5H2O, a new Ni analogue of 40
hydromagnesite associates with hydrothermal nickel deposit [9] and takovite is a 41
nickel hydroaluminate with composition Ni6Al2(CO3,OH) (OH)16.4H2O [10,11]. 42
There are a significant number of nickel carbonates with mixed cations especially 43
with a layered double hydroxide (LDH) structure which include carboydite, 44
comblainite, mountkeithite, reevesite and takovite [12-18]. It is important to study the 45
gaspeite-hellyerite-nullaginite assemblage and the relative stability of the minerals. 46
The reason is that these minerals are the stable minerals at one atmosphere. 47
48
Nullaginite Ni2(CO3)(OH)2 is closely related to rosasite and glaukosphaerite, 49
occurs as bright green nodular grains in a Ni-rich assemblage from the Otway deposit, 50
Nullagine district, Western Australia [1]. Several phases can be grouped into the 51
malachite-rosasite group minerals, with a general formula M22+(CO3)(OH)2 that 52
includes malachite (M22+ = Cu) and rosasite ( M2
2+ = Cu,Zn) together with rare species 53
like mcguinnessite (Mg,Cu), glaukosphaerite (Cu,Ni), nullaginite (Ni) and zaratite 54
(Ni) [19]. The crystal structure determination of rosasite and mcguinnessite from 55
powder data shows they are isostructural, with space group P21/a, and cell constants a 56
= 1.2898, b = 0.9371 and c = 0.3162 nm for rosasite and a = 1.2918, b = 0.9392 and c 57
= 0.3162 nm for mcguinnessite. It has been shown that the structures of both 58
malachite and rosasite are built up by “octahedral” walls of edge-sharing M22+ 59
polyhedra, linked together through corner sharing to form infinite layers, and 60
“triangular” CO3 groups, which assure their interlayer connection. Two distinct 61
models are realised in this mineral group and are denoted as malachite-like and 62
rosasite-like structures [20]. 63
64
Four samples of natural takovite from different origins were examined by X-65
ray powder diffraction and chemical analysis. The observed cell parameters are 66
3
closely similar to those of pyroaurite and hydrotalcite [11]. The XRD pattern of 67
widgiemoolthalite, from Western Australia [9] suggests a high degree of structure 68
disorder and the cell parameters similar to that of hydromagnesite with a = 1.006, b = 69
0.875 and c = 0.832 nm. The minerals of the pyroaurite and sjogrenite group 70
represented by a common formula Mg6Fe2(OH)16(CO3).4H2O form hexagonal, platy 71
crystals. In other members of the group, Mg2+ may be replaced by dipositive cations 72
of similar size for example, Ni2+ and Fe3+ by suitable tripositive cations like Al3+, Cr3+ 73
[21]. 74
Infrared and Raman spectroscopy have been applied to investigate carbonates. 75
A detailed single crystal Raman study of selected mineral carbonates has been 76
undertaken [22-28]. This would seem to be important in the context of the stability of 77
the hydroxy carbonates of Ni, Zn, Cu and Pb. However electronic and vibrational 78
spectroscopy of many carbonates of Ni has not been undertaken. This may be due to 79
the unknown structure of some nickel hydroxy carbonates. Few infrared spectral 80
studies of related minerals such as the rosasite group have been forthcoming [29-31]. 81
82
Carbonate minerals produce absorption features from visible-near-infrared to 83
thermal infrared spectral regions. Structural variations accompanied by the 84
substitution of Mg2+ or Ca2+ by other divalent cations like Cu2+ , Co2+, Ni2+, Fe2+ can 85
be studied through the electronic spectral features in UV-Vis-NIR region. These 86
spectra can be used for the determination of the coordination state of transition metals 87
in minerals [32-36]. Several strong bands due to vibrations of the carbonate radical 88
and OH units occur in NIR and IR regions [37-40]. Recent studies have shown that 89
the formation of secondary precipitates plays an important role in the retention of Ni 90
and Co by clay minerals. It is evident that a precise knowledge of the nature of these 91
precipitates is crucial to predict the fate of Ni and Co in the environment, because of 92
the solubility of the precipitates strongly depends on their structure and composition 93
[41-43]. Several studies have already been reported concerning optical absorption 94
spectra Ni-hydrous silicates [44-46] and Ni-carbonate minerals of zaratite and 95
takovite have been published [47]. Subsequently Ni in clay minerals has been 96
preciously studied to know the mechanism of Ni-Mg substitution [41,48]. 97
98
Spectroscopic properties of nickel bearing carbonates and silicates are still 99
quite lacking. In this paper we present the results of a systematic study of nickel-100
4
bearing carbonate minerals and compare the spectral properties with their structure 101
and composition. 102
103
2. Experimental 104
105
2.1. Sample description 106
107
The minerals used in this work are nullaginite (bright green), 108
widgiemoolthalite (bluish green) and takovite (pale green) were kindly supplied by 109
CSIRO, Australia and zaratite (green) was procured from Mineralogical Research 110
Co., U.S.A. The characterisation and composition of these minerals has already been 111
established and published. 112
113
2.2. UV-Vis spectroscopy 114
115
A Varian Cary 5000 UV-Visible NIR spectrophotometer, equipped with 116
Diffuse Reflectance Accessory (DRA) was employed to record the electronic 117
spectrum of the samples in the region between 200 and 1100 nm (50,000-9090 cm-1). 118
This technique allows the study of the reflectance spectra of the samples in the 119
powder form. The DRA consists of a 110 mm diameter integrating sphere, featuring 120
an inbuilt high performance photomultiplier. Each sample was placed in a powder cell 121
specifically designed for the instrument. Initially a base line was recorded using a 122
polytetrafluoroethylene (PTFE) reference cell covering the reflectance port. The 123
sample is then mounted over the port and the reflection off the sample surface was 124
collected by the sphere. The reflectance was therefore measured relative to the PTFE 125
disk. The diffuse reflectance measurements were converted into absorption (arbitrary 126
units) using the Kubelka-Munk function (f (R ) = (1- R )2/2R ). Data manipulation was 127
performed using Microsoft Excel. 128
2.3. Near-infrared (NIR) spectroscopy 129
130
NIR spectra were collected on a Nicolet Nexus FT-IR spectrometer with a Nicolet 131
Near-IR Fibreport accessory (Madison, Wisconsin). A white light source was used, 132
with a quartz beam splitter and TEC NIR InGaAs detector. Spectra were obtained 133
5
from 13,000 to 4000 cm-1 (0.77-2.50 µm) (770-2500 nm) by the co-addition of 64 134
scans at a spectral resolution of 8 cm-1. A mirror velocity of 1.266 m sec-1 was used. 135
The spectra were transformed using the Kubelka-Munk algorithm to provide spectra 136
for comparison with published absorption spectra. 137
138
Spectral manipulation such as baseline adjustment, smoothing and 139
normalisation were performed using the Spectracalc software package GRAMS 140
(Galactic Industries Corporation, NH, USA). Band component analysis was 141
undertaken using the Jandel ‘Peakfit’ software package which enabled the type of 142
fitting function to be selected and allows specific parameters to be fixed or varied 143
accordingly. Band fitting was done using a Lorentz-Gauss cross-product function with 144
the minimum number of component bands used for the fitting process. The Gauss-145
Lorentz ratio was maintained at values greater than 0.7 and fitting was undertaken 146
until reproducible results were obtained with squared correlations of r2 greater than 147
0.995. 148
149
3. Results and discussion 150
151
3.1. Nullaginite and zaratite 152
153
The six-fold coordination of Ni2+ in serpentine and talc [49], chrysotile [50], 154
nickel antimony sulphide mineral, ulmannite [51] and gaspeite [52] was established 155
from the study of optical absorption spectra of Ni-bearing minerals. The reflectance 156
spectra of the four Ni carbonate minerals were recorded using Varian Cary 5000 UV-157
Visible NIR spectrophotometer and transformed into absorbance coefficients using 158
the Kubelka-Munk function. The spectra have been decomposed by Gaussian analysis 159
to obtain each spectral feature corresponding to a band component and are illustrated 160
(for each sample). Three bands are expected for Ni2+ in an octahedral field [53]: 161 3A2g(
3F) 3T1g(3P) (1 band), 3A2g(
3F) 3T1g(3F) (2 band) and 3A2g(
3F) 3T2g(3F) 162
(3 band). The spectra of nullaginite and zaratite show three main features which are 163
characteristic of the presence of divalent nickel ion in six-fold coordination. The 164
spectral patterns of the two minerals are shown in Figs. 1, 2 and 3. Three broad 165
intense bands centred at 25955, 15230 and 9190 cm-1 in nullaginite are assigned to 166
6
spin-allowed transitions, 3A2g(3F) 3T1g(
3P), 3A2g(3F) 3T1g(
3F) and 3A2g(3F) 167
3T2g(3F). In addition, a prominent shoulder on the low wavenumber side of 2 band 168
arising from the spin-forbidden transition 3A2g(3F) 1Eg(
1D), invariably appeared in 169
all the four Ni-carbonates. For nullaginite the spin-forbidden transition is located at 170
13200 cm-1. The crystal field and Racah parameters, Dq and B are determined from 171
the observed band positions using the energy expressions [54]: 172
173 3A2g(
3F) 3T1g(3P): 15Dq + 13.5B = 25955 cm-1 (1) 174
3A2g(3F) 3T1g(
3F): 15Dq + 1.5B = 15230 cm-1 (2) 175
and 3A2g(3F) 3T2g(
3F): 10Dq = 9190 cm-1 (3) 176
B = 894 cm-1 is obtained from the relation, 1 - 2 = (25955 - 15230 cm-1) = 12B and 177
Dq = 919 cm-1 is a direct measure of crystal field parameter from 3. The ratio of 178
Dq/B has been used to determine the transition for the 29830 cm-1 band in the UV 179
region from the energy level diagram of d8 configuration (Ni2+) as 3A2g(3F) 1Eg(
1G) 180
[55]. 181
The spectral patterns of the two minerals look similar. The position and 182
intensity of the bands slightly vary from one another. Zaratite bands observed at 183
25855 (1-band), 14740 (2-band) and 9145 cm-1 (3-band) are assigned to the three 184
spin-allowed transitions of 3A2g(3F) 3T1g(
3P), 3A2g(3F) 3T1g(
3F) and 3A2g(3F) 185
3T2g(3F). The shoulder band extended to the 2 main band at13380 cm-1 is identified as 186
3A2g(3F) 1Eg(
1D) transition. The parameters evaluated from the zaratite bands are 187
Dq = 915 and B = 926 cm-1. The 1- and 3-bands show pure Gaussian shape as 188
observed in nickel hydroxide and nickel-doped ammonium-magnesium double 189
sulphate ( Tutton salt) and the absence of splitting confirms a regular octahedral 190
symmetry (Oh) for Ni2+ [56]. The line shape of the 3-band is particularly sensitive to 191
the site symmetry because of its dependence on the crystal field. The half-width (2800 192
cm-1) of 3 band in zaratite is slightly more than the half-width (2700 cm-1) observed 193
for nullaginite (Fig. 3). The result of non-Gaussian shape and splitting of the 3 band 194
into two main component bands; 9190 and 7880 cm-1for nullaginite and 9145 and 195
7910 cm-1 in zaratite may be assigned to the lowering of Ni-site to either tetragonal or 196
trigonal. 197
198
7
The spectra of the two hydroxyl-bearing nickel carbonates presented in Figs. 3 199
and 4 show OH overtone and combination bands resulting from structural hydroxyls 200
and water. A single band at 6845 cm-1 for OH overtone is seen in zaratite where as in 201
nullaginite this band appeared with structure at 7185-6745 cm-1. The difference in the 202
spectra may be explained by the compositional variations between the two carbonates 203
[57]. An observation of two strong OH vibrational modes in IR at 3600-3400 cm-1 and 204
the overtones of OH fundamentals around 7000 cm-1 in near-IR have been made in a 205
number of carbonate minerals [58-62]. Visible and near-infrared spectra of minerals 206
and rocks reported by Hunt and Salisbury [63] show a strong band at 5260 cm-1 which 207
is used as evidence of liquid water in minerals. Near-IR spectra in Fig. 4 show a broad 208
band from 4945-5155 cm-1 due to the presence of water both in nullaginite and 209
zaratite. The carbonate ion displays a strong absorption feature in the low 210
wavenumber region. The unsymmetrical band near 4300 cm-1 assigned to the 211
combination of the vibrational modes of CO32- is evidence for the reduction in 212
symmetry for carbonate ion. 213
214
3.2. Widgiemoolthalite and takovite 215
216
The electronic and vibrational spectra in the UV-Vis and NIR regions are 217
shown in Figs. 5, 6, 7 and 8. Notably, as can be expected from their structural 218
formulae difference, the spectral features of the carbonates-widgiemoolthalite 219
(Ni,Mg)5(CO3)4(OH)2.5H2O and takovite Ni6Al2(CO3,OH)(OH)16.4H2O are not 220
similar. The spectra in Fig. 5 allow us to extract cation-ordering information relevant 221
to the samples. The decomposition of the spectral patterns of widgiemoolthalite 222
exhibits three main bands in at 26200 (1), 15010 (2) and 9185 cm-1 (3), together 223
with spin-forbidden bands of low intensity band in the visible range at 20580 and the 224
shoulder to 2 band appear at 13760 cm-1. For takovite, the 1, 2 and 3 bands are 225
observed at 26720, 15140 and 9200 cm-1 while the spin forbidden bands appeared at 226
20540 and 13380 cm-1. Dq and B parameters obtained from the observed energies of 227
the bands are 918 and 932 cm-1 for widgiemoolthalite whereas in takovite these values 228
are 920 and 965 cm-1. The half-width of 3 band measured for widgiemoolthalite as 229
3150 cm-1 is larger than that for (2700 cm-1) takovite (Fig. 7). 230
231
8
The relative values of ∆○ obtained from the energy of the 3A2g(3F) 3T2g 232
transition allow us to calculate Crystal Field Stabilization Energy (CFSE) of nickel in 233
the four samples studied. There are two main features in the NIR spectra (Fig. 8) as a 234
function of band frequency in the ranges: >5000 and <4500 cm-1. In the former region 235
we observe absorptions due to occupied water molecules in the minerals and the 236
latter, strong absorption band is due to CO32- ion. The splitting of 1 and 3 bands and 237
non-Gaussian shape of 3-band in the minerals are the effects of Ni-site distortion 238
from the regular octahedron. For each band, the values obtained notably, wavenumber 239
are nearly similar but relative intensity is different for the two carbonates (Table 2 and 240
3). The small differences can be attributed to the main reasons: (1) the slight chemical 241
differences between the samples [9,11] and (2) the structural cation substitution 242
(Mg2+, Ni2+, Fe2+) and trivalent cations like Al3+, Fe3+. The absence of UV band in 243
takovite may be explained by the presence Al significantly in the mineral [11]. The 244
position and assignments of the bands of Ni-bearing carbonates are compared with the 245
data reported for other carbonates, zaratite: Oxford serpentine quarry, Texas, USA; 246
takovite: Carr Boyd Nickel Mine, Australia; nickel hydroxide and kerolite from New-247
Caledonia in Table 2 and crystal field parameters in Table 3. The structural cation 248
substitutions, like Mg2+, Ni2+, Fe2+ and trivalent cations, Al3+, Fe3 in the Ni-249
carbonates cause band shifts to high wavenumbers with reference to nickel hydroxide 250
(Table 2) and the shift is more significant for widgiemoolthalite 251
(Ni,Mg)5(CO3)4(OH)2.5H2O and takovite Ni6Al2(CO3,OH)(OH)16.4H2O. Table 3 252
shows the CFSE values vary in the range >10560 and <11040 cm-1. The increase of 253
CFSE value indicates the intensity of distortion of Ni-site in the carbonate minerals 254
studied. 255
256
257
4. Conclusions 258
259
Spectroscopic analysis of Ni carbonates is in harmony with chemical 260
composition confirming the presence of both molecular water and carbonate ions in 261
the mineral structure. Three broad intense bands centred at 26720-25855 cm-1(1), 262
15230-14740 cm-1(2) and 9200-9145 cm-1(3) are assigned to spin-allowed 263
transitions, 3A2g(3F) 3T1g(
3P), 3A2g(3F) 3T1g(
3F) and 3A2g(3F) 3T2g(
3F). In 264
9
addition, a prominent shoulder on the low wavenumber side of the 2 band arising 265
from the spin-forbidden transition 3A2g(3F) 1Eg(
1D), invariably appeared in all the 266
four Ni-carbonates. The relative values of ∆○ obtained directltly from the observed 267
energy of the 3A2g(3F) 3T2g(
3F) transition allow us to calculate Crystal Field 268
Stabilization Energy (CFSE) of nickel in the four mineral samples studied. The value 269
of CFSE indicates the degree of distortion of Ni-site in the carbonate minerals studied. 270
The result of non-Gaussian shape and splitting of the 3 band around 9200 cm-1 in 271
NIR spectra of the Ni-carbonates suggests lowering of Ni-site from regular octahedral 272
to either tetragonal or trigonal. A broad unsymmetrical band in the NIR spectra 273
centred in the range 4225-4425 cm-1 is the result of symmetry distortion of CO32- ion 274
in the Ni-carbonate-bearing minerals. Band shifts are caused due to structural cation 275
substitutions (Mg2+, Ni2+, Fe2+ and trivalent cations, Al3+, Fe3) in the carbonate 276
minerals studied and shift is more significant for widgiemoolthalite 277
(Ni,Mg)5(CO3)4(OH)2.5H2O and takovite Ni6Al2(CO3,OH)(OH)16.4H2O. 278
279
Acknowledgements 280
281
The financial and infra-structure support of the Queensland Research and 282
Development Centre (QRDC-Alcan) and the Queensland University of 283
Technology Inorganic Materials Research Program of the School of Physical and 284
Chemical Sciences is gratefully acknowledged. The Queensland University of 285
Technology is also acknowledged for the award of a Visiting Fellowship to B. 286
Jagannnadha Reddy. 287
288
289
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[60] R. L. Frost, D.L. Wain, W.N. Martens, B. J. Reddy, Spectrochim. Acta Part A 369
66 370
(2007) 1068. 371
[61] R. L. Frost, B. J. Reddy, D.L. Wain, W.N. Martens, Spectrochim.Acta Part A 66 372
(2007) 1075. 373
[62] R.L. Frost, D. L. Wain, W.N. Martens, B. J. Reddy, Polyhedron 26 (2007) 275. 374
[63] G.R. Hunt, J.W. Salisbury, Mod. Geol. 5 (1976) 211. 375
[64] A. Manceau, G. Calas, A. Decarreau, Clay Miner. 20 (1985) 367. 376
377
378
379
13
380
Code
Mineral
Colour
Formula
Origin
Ni-1
Nullaginite
Bright green
Ni2(CO3)(OH)2
Otway Prospect, Nullagine Region,
Western Australia
Ni-2 Zaratite Green
Ni3(CO3)(OH)4.4H2O
Lord Brassey Nickel Mine,
Heazlewood, Tasmania, Australia
Ni-3 Widgiemoolthalite Bluish green
fibres
(Ni,Mg)5(CO3)4(OH)2.5H2O
132 North Nickel Mine,
Widgiemooltha, Co., Western Australia
Ni-4 Takovite Pale green Ni6Al2(CO3,OH)(OH)16.4H2O
Perseverance Nickel Deposit, Agnew,
Western Australia
381
382
Table 1 Table of the Ni carbonate-bearing minerals, their origin and formula 383
14
Nullaginite Ni2(CO3)
(OH)2
(cm-1)
Present study
Zaratite Ni3(CO3)
(OH)4.4H2O
(cm-1)
Present study
Widgiemoolthalite
(Ni,Mg)5(CO3)4
(OH)2.5H2O
(cm-1)
Present study
Takovite
Ni6Al2(CO3,OH)
(OH)16.4H2O
(cm-1)
Present study
Nickel
hydroxide
Ni(OH)2
(cm-1)
Reported [64]
Kerolite
(Mg,Ni)3Si4O10
(OH)2.H2O
(cm-1)
Reported [64]
Zaratite Ni3(CO3)
(OH)4.4H2O
(cm-1)
Reported [47]
Takovite
Ni6Al2(CO3,OH)
(OH)16.4H2O
(cm-1)
Reported [47]
Suggested assignment
29830
30970c
29660
30490
nd
3A2g(3F) 1Eg(
1G) t
25955
25855
26200
25410c
26720
23860c
25700
23560
25800
23900
23805
26665
3A2g(3F) 3T1g(
3P) t
nd
nd
20580
20540
22300
22340
21735
24095
3A2g(3F) 1T2g(
1D) t
15230
14740
15010
15140
15040
17320
15380
14285
15380
3A2g(3F) 3T1g(
3F) t
13200sh
13380sh
13090sh
13380sh
13240
13580
nd
14930
3A2g(3F) 1Eg(
1D) t
9190
7880sh
9145
7910sh
9185
7820sh
9200
8075sh
8800
8950
8195
10000
8200
3A2g(3F) 3T2g(
3F) t
15
7185c
6745
6845
6785
6405
6885
6505sh
nr nr 7140 7-90 22 a
22 a
22 a
5085
5155
4945sh
5645sh
5130
5380sh
5155
4910sh
nr
nr
nr
nr
(2 + 3) a
(2 + 3) a
(2 + 3) a
4315 4225 4425 4310 nr nr nr nr (23 + 24) b
384 t Electronic transition of Ni2+ 385 a Overtones and combination modes of OH fundamentals; 3 and 2 observed in IR at 3500-3300 and 3000-2800 cm-1. 386 b Overtones and combination modes of (CO3)
2- fundamentals observed in IR (1 = 1045, 2 = 830, 3 = 1510 and 4 = 740 cm-1) 387 Abbreviations: p-component; sh-shoulder; nd-not detected 388 389
390
391
Table 2 Assignments of the UV-Vis and NIR bands of Ni carbonate bearing-minerals and other Ni compounds. 392
16
Table 3 Comparison of crystal field parameters of Ni2+ in Ni-carbonates with 393
other complexes 394
395
Complex
Transition energy
[3A2g(3F) 3T2g(
3F)]
(10Dq = ∆○)
(cm-1)
CFSE
(6/5)∆○)
(cm-1)
Reference
Tutton salt
[M2M'(SO4)2.(H2O)6]
8850 10620 [63]
Nickel hydroxide
Ni(OH)2
8800 10560 [63]
Kerolite
(Mg,Ni)3Si4O10(OH)2.H2O
8950 10740 [63]
Gaspeite
Ni,Mg,Fe)(CO3)
8130 9756 [52]
Zaratite
Ni3(CO3)(OH)4.4H2O
8195 9834 [47]
Takovite
Ni6Al2(CO3,OH)(OH)16.4H2O
9100 10920 [47]
Nullaginite
Ni2(CO3)(OH)2
9190 11028 Present study
Zaratite
Ni3(CO3)(OH)4.4H2O
9145 10974 Present study
17
Widgiemoolthalite
(Ni,Mg)5(CO3)4(OH)2.5H2O
9185 11022 Present study
Takovite
Ni6Al2(CO3,OH)(OH)16.4H2O
9200 11040 Present study
396
397
398
399
400
18
List of Tables 401
402
Table 1 Table of the Ni carbonate-bearing minerals, their origin and formula 403
404
Table 2 Assignments of the UV-Vis and NIR bands of Ni carbonate bearing-405
minerals and other Ni compounds. 406
407
Table 3 Comparison of crystal field parameters of Ni2+ in Ni-carbonates with 408
other complexes 409
410
List of Figures 411
412
Fig. 1 UV-Visible-NIR spectra of nullaginite and zaratite: 300-420 nm region. 413
414
Fig. 2 UV-Visible-NIR spectra of nullaginite and zaratite: 550-800 nm region. 415
416
Fig. 3 Near-infrared (NIR) spectra of nullaginite and zaratite: 11000-6000 cm-1 417 region. 418
419
Fig. 4 Near-infrared (NIR) spectra of nullaginite and zaratite: 6000-4200 cm-1 420 region. 421
422
Fig. 5 UV-Visible-NIR spectra of widgiemoolthalite and takovite: 300-550 nm 423
region. 424
425
Fig. 6 UV-Visible-NIR spectra of widgiemoolthalite and takovite: 500-800 nm 426
region. 427
428
Fig. 7 Near-infrared (NIR) spectra of widgiemoolthalite and takovite: 11000- 429
6000 cm-1 region. 430
431
Fig. 8 Near-infrared (NIR) spectra of widgiemoolthalite and takovite: 6000-4000 432
cm-1 region. 433
434
19
435
436
437
438
439
440
441
442
443
20
444
Figure 1 445
446
447
448
449
450
451
452
453
454
21
455
456
Figure 2 457
458
459
22
460
461
462
Figure 3 463
464
23
465
466
Figure 4 467
468
24
469
470
471
472
473
Figure 5 474
475
476
25
477
478
Figure 6 479
480
26
481
482
483
Figure 7 484
485
486
27
487
488
Figure 8 489
490
491
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