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ISSN 1063-7745, Crystallography Reports, 2008, Vol. 53, No. 3, pp. 391–397. © Pleiades Publishing, Inc., 2008.
Original Russian Text © V.I. Rozhdestvina, A.V. Ivanov, M.A. Zaremba, O.N. Antsutkin, W. Forsling, 2008, published in Kristallografiya, 2008, Vol. 53, No. 3, pp. 423–430.
391
INTRODUCTION
For platinum as a mineral-forming element, 64 min-
erals were found. Eleven platinum minerals do not have
their own names [1]. Eighteen minerals belong to sul-
fides, in which Pt is associated with Pd, Ir, Rh, Cu, Ni,
Fe, Co, and Pb. Of the most abundant minerals, two sul-
fide minerals, cooperite (PtS) and braggite ((Pt,Pd)S,
belong to the same isomorphous series, in which the
platinum content gradually decreases, the palladium
content gradually increases, and a nickel impurity is
often present [2]. However, the discontinuity in the
metal content is indicative of the discreteness of this
series. Cooperite, which is one of the main sources of
platinum in copper–nickel sulfide ores, generally crys-
tallizes in the following two morphological modifica-
tions: irregular grains and, more rarely, micron- and
submicron-size prismatic crystals in association with
iron varieties of platinum and osmium–iridium miner-
als. Single-crystalline mineral grains of cooperite are
very rare in occurrence. Such crystals were found in
deposits in the Far-East.
In the present study, single-crystalline samples of
cooperites, which were found in placers from the Yuna-
Dan’sk gold-ore cluster of the platinum-bearing prov-
ince in the Sea of Okhotsk region of the Ma
œ
makansk
zone in the Far East, were studied by electron micros-
copy, electron-probe X-ray microanalysis, X-ray dif-
fraction, and magnetic resonance spectroscopy (ESR
and
195
Pt static and MAS NMR spectroscopy). This
gold-ore cluster is characterized by the presence of
large amounts of idiomorphic single-crystalline min-
eral grains of cooperite in association with ferrous vari-
eties of platinum, osmium–iridium minerals, and palla-
dium stibnites and arsenides. The paragenesis of coo-
perite single crystals and high-temperature platinum-
group minerals could be formed under high-tempera-
ture conditions and, consequently, under conditions
where sulfur exhibits high chemical activity. Xenomor-
phic inclusions of cooperite are prone to be located at
the periphery of mineral grains, thus filling microcavi-
ties and microcracks, which is evidence that cooperite
is a secondary mineral. This is confirmed by the data
[3, 4] on the chemical modeling of the formation of
cooperite even under rather mild conditions. In contrast
to other platinum-bearing ore clusters in the Far East
(containing predominantly minerals, which are inter-
metallic ordered and disordered varieties of platinum–
ferrous and osmium–iridium–ruthenium solid solutions
[5], and sometimes platinum arsenides, such as sper-
rylite (PtAs
2
) [6]), this ore cluster is characterized by
the pronounced platinum sulfide and stibiopalladinite
mineral reduction. The latter is indicative of specific
(even within the platinum-bearing province in the Sea
of Okhotsk region) local conditions of the genesis of
platinum-group minerals for the ore cluster under con-
sideration.
Single-Crystalline Cooperite (PtS): Crystal-Chemical
Characterization, ESR Spectroscopy,
and
195
Pt NMR Spectroscopy
V. I. Rozhdestvina
a
, A. V. Ivanov
a
, M. A. Zaremba
a
,
O. N. Antsutkin
b
, and W. Forsling
b
a
Institute of Geology and Nature Management, ul. B. Khmel’nitskogo 2,
Far East Division, Russian Academy of Sciences, Blagoveshchensk, 675000 Russia
e-mail: veronika@ascnet.ru
b
Luléa University of Technology, SE-971 87 Luléa, Sweden
Received December 11, 2006; in final form, December 3, 2007
Abstract
—Single-crystalline cooperite (PtS) with a nearly stoichiometric composition was characterized in
detail by X-ray diffraction, electron-probe X-ray microanalysis, and high-resolution scanning electron micros-
copy. For the first time it was demonstrated that
195
Pt static and MAS NMR spectroscopy can be used for study-
ing natural platinum minerals. The
195
Pt chemical-shift tensor of cooperite was found to be consistent with the
axial symmetry and is characterized by the following principal values:
δ
xx
= –5920 ppm,
δ
yy
= –3734 ppm,
δ
zz
=
+4023 ppm, and
δ
iso
= –1850 ppm. According to the ESR data, the samples of cooperite contain copper(II),
which is adsorbed on the surface during the layer-by-layer crystal growth and is not involved in the crystal lat-
tice.
PACS numbers:
61.50.
Nw
, 61.66.-
f
DOI:
10.1134/S106377450803005X
DIFFRACTION AND SCATTERING
OF IONIZING RADIATIONS
392
CRYSTALLOGRAPHY REPORTS
Vol. 53
No. 3
2008
ROZHDESTVINA et al.
EXPERIMENTAL
The morphological and microstructural features of
cooperite samples, the phase microinhomogeneity, and
the chemical composition were studied by electron
microscopy and electron-probe X-ray microanalysis.
The qualitative determinations of elements based on the
phases were performed by electron-probe X-ray
microanalysis on a RONTEC energy-dispersive spec-
trometer equipped with a LEO-1420 scanning electron
microscope. The quantitative determinations were car-
ried out by the ZAF-correction method on a 35-SDS
wavelength-dispersive spectrometer equipped with a
JSM-35C JEOL scanning electron microscope with the
use of chemically pure platinum and standardized sul-
fides (PtS and PbS) as reference samples. The morphol-
ogy, microstructures, and the phase microinhomogene-
ity were studied using different modes for the detection
of secondary and reflected electrons. The accelerating
voltage and the current passing through the samples
were chosen according to the problem at hand.
The structures of natural samples of platinum sul-
fide were studied by X-ray diffraction on an URS-2.0
instrument (Ni-filtered Cu-
K
α
radiation) by rotating a
single crystal about the principal axes. The layer lines
in the X-ray diffraction patterns were processed with
the use of a computer program based on the extraction
of the data on the optical density of X-ray films fol-
lowed by their storage as the full-profile two-coordinate
representation
I
(2
θ
)
. The algorithm works in the high-
precision range of the determination of the crystal-lat-
tice parameters with separated diffraction maxima cor-
responding to the
K
α
1
and
K
α
2
spectral lines. The unit-
cell parameters were calculated by the least-squares
method using the autoindexing program. The X-ray
powder diffraction patterns were measured on a
DRON-3 diffractometer (Ni-filtered Cu-
K
α
radiation)
from a rotating sample using the step-scan technique
with a
τ
-scan step
τ
= 0.01° 2
θ
. The exposure time per
step was 10 s. The parameters were determined and the
overlapping peaks were separated by the approxima-
tion method using graphical editors and analyzers for
X-ray diffraction patterns. The autoindexing and refine-
ment of the parameters were carried out with the use of
the PDWin program package (NPP Burevestnik). The
theoretical X-ray diffraction pattern was calculated
with the use of the POWDER CELL program [7].
195
Pt static and MAS NMR spectra
were recorded on
a CMX-360 pulse spectrometer (Varian/Chemagnetics
InfinityPlus, United States) in the operating-frequency
range of 76.909–77.709 MHz equipped with a superon-
ducting magnet (
B
0
= 8.46 T) and with the use of the
Fourier-transform technique. The magic-angle-spin-
ning (MAS) spectra were recorded using the excitation
pulse of
67.5°
with a delay time of 1.5
µ
s, which corre-
sponds to the excitation bandwidth of 125 kHz. The
total width of the experimental
195
Pt MAS NMR spec-
trum (on the frequency scale) was ca. 0.8 MHz. Since it
was impossible to achieve the simultaneous excitation
of the total NMR spectrum, the spectrum was recorded
in fragments with a frequency step of 100 kHz followed
by the summation of individual fragments. The
195
Pt
static and MAS NMR spectra were recorded from coo-
perite samples with a weight of ca. 310 mg, which were
placed in zirconium dioxide rotors with a diameter of
4.0 mm (in the former case, because of high structural
ordering, the samples were thoroughly ground; in the
latter case, natural single-crystalline mineral grains
were used). The samples were spun at the magic angle
at a spinning frequency of 8000(1) Hz. For each region
of the MAS spectrum, the number of acquisitions was
300. The time delay between the excitation pulses was
4.0 s. The static spectra were obtained in fragments
with a step of 100 kHz using a spin-echo pulse sequence
(
90°
–
τ
–
80°
–
τ
) with a pulse length of 2.0 and 4.8
µ
s,
respectively, and a delay time
τ
= 160
µ
s. For each
region of the static spectrum, the number of acquisi-
tions was 4512, and the time delay between the excita-
tion pulses was 4 s. Since the beginning of the interfer-
ence patterns (free-induction decay, FID) for the MAS
spectra was distorted by the attenuated excitation pulse
(due to the ring-down), the distorted region was sub-
tracted. Then, to avoid phase distortions of the MAS
NMR spectra, the interference pattern was shifted
toward the attenuation region to the required number of
points before performing the Fourier transform. Since
the interference patterns included 15 spin-echo pulses,
the subtraction of the initial fragment did not lead to
critical distortions of the spectra. The
195
Pt isotropic
chemical shift and the principal values of the
195
Pt
chemical-shift tensor are given with respect to a 0.1 M
aqueous H
2
[
PtCl
6
]
solution (Merck), 0 ppm [8], which
corresponds to the resonance frequency (77.3778 MHz)
of
195
Pt nuclei. The homogeneity of the magnetic field
was monitored based on the width of the reference line
of crystalline adamantane at
δ
(
13
C
)
= 38.56 ppm
(2.4 Hz). The parameters of the
195
Pt NMR spectrum
were corrected for the drift of the magnetic-field
strength in the course of experiments, whose frequency
equivalent for
195
Pt nuclei was 0.044 Hz/h. The magic
angle was set at the resonance frequency of the
79
Br
nuclide (90.189 MHz) according to a standard proce-
dure with the use of crystalline KBr. The additional
adjustment was performed to achieve the minimum lin-
ewidths in the
195
Pt MAS NMR spectrum of cooperite.
ESR spectra
were recorded on a 70-02 XD/1
radiospectrometer (MP CZ, Minsk) operating at
ca. 9.5 GHz at
~295
K. The operating frequency was
measured with a ChZ-46 microwave frequency meter.
The
g
factors were calculated relative to diphenylpic-
rylhydrazyl (DPPH). The errors of the determination of
the
g
factors and the hyperfine-structure constants
(given in Oe) are
±
0.002
and
±
2%
, respectively. To
reveal fine details, the double differentiation of the
experimental spectra was carried out. The ESR spectra
were simulated within the second-order perturbation
theory with the WIN-EPR SimFonia program (version
CRYSTALLOGRAPHY REPORTS
Vol. 53
No. 3
2008
SINGLE-CRYSTALLINE COOPERITE (PtS): CRYSTAL-CHEMICAL CHARACTERIZATION 393
1.2, implemented in the Bruker software). In the course
of fitting of the model spectra to the experimental spec-
tra, the
g
factors, the hyperfine- structure constants, the
resonance linewidths, and the Lorentz and Gaussian
contributions to the line shape were varied.
RESULTS AND DISCUSSION
Electron-Microscopic and Electron-Probe X-ray
Microanalysis Data
Cooperite from the Yuna-Dan’sk gold-ore cluster
exists primarily as idiomorphic black single-crystalline
mineral grains with metallic lustre and conchoidal frac-
ture. The grains are crystal-faceted, their faces are
hatched, and the grains are often characterized by the
rhombic geometry (Fig. 1a). Single crystals are often
chipped. Individual grains with smoothed edges and
traces of dissolution were found (Figs. 1b and 1c). The
average size of single-crystalline mineral grains is 200–
300
µ
m. Individual grains with sizes larger than 1 mm
were found (Fig. 1d). This variety of cooperite corre-
sponds in chemical composition to platinum sulfide
(Fig. 2) having the following stoichiometric composi-
tion: Pt, 85.826 wt %; S, 13.917 wt %. Insignificant iron
impurities were found in some samples. The amounts
of Pd, Ni, and some other elements are outside the sen-
sitivity limits of electron-probe X-ray microanalysis
(a wavelength-dispersive spectrometer). In addition, it
should be noted that no inclusions of impurity phases in
cooperite single crystals were revealed at the micron
and submicron level. It was found that the composition
of cooperite differs from the stoichiometric composi-
tion in that certain samples are either deficient or rich in
platinum (Table 1). The Pt-to-S ratio varies in the range
of 5.18–7.54, compared to 6.08 for the cooperite refer-
ence sample. The generalized crystal-chemical formula
for the cooperite samples under study can be written as
Pt
1 –
x
S
1 +
x
(
−
0.1
≤
x
≤
+0.1)
.
X-ray Diffraction Data
Cooperite (PtS) crystallizes in the tetragonal system
(sp. gr.
P
4
2
/
mmc
). Its structure can be described as a tet-
ragonally distorted (
c
/2
a
= 0.88) cubic packing formed
by S atoms (the unit-cell height is equal to the height of
two such pseudo-unit cells). The sulfur atoms in coo-
perite are surrounded by four platinum atoms occupy-
ing the vertices of a slightly distorted tetrahedron. The
Pt atoms occupy two crystallographically independent
sites and are arranged so that the opposite faces of two
pseudocubic unit cells comprising the cooperite struc-
ture are centered (Fig. 3a). In both cases, the metal
atoms are in the square-planar environment formed by
four sulfur atoms to give the chromophore [PtS
4
]
(Fig. 3b).
The X-ray diffraction pattern of single-crystalline
cooperite was, on the whole, indexed within the tetrag-
onal unit cell (sp. gr.
P
4
2
/
mmc
) with the most often
observed parameters
a
= 3.4695(2) Å,
c
= 6.1066(9) Å,
c
/2
a
= 0.088 Å,
V
= 73.508(5) Å
3
, and
ρ
= 10.263 g/cm
3
.
The experimental X-ray powder diffraction patterns
100 µm 30 µm
30 µm 100 µm
(a) (b)
(c) (d)
Fig. 1.
Crystal morphology of cooperite. (a) A single-crys-
talline grain with hatched faces. Individual grains with
(b) smoothed edges and (c) traces of dissolution. (d) Single
crystals of dimensions larger than 1 mm.
1000
0 4 8 12 16 20
E
, keV
2000
3000
4000
5000
I, rel. units
PtMα
SKα
PtLα
PtLβPtLγ
Fig. 2. Energy-dispersive spectrum of cooperite single crys-
tals.
394
CRYSTALLOGRAPHY REPORTS Vol. 53 No. 3 2008
ROZHDESTVINA et al.
(measured from 20 mineral grains ground to powder)
contain 42 reflections, which are in good agreement
with the calculated data (the POWDER CELL program
[7]). The set of interplanar spacings corresponds to the
PtS phase (PDF 18-972) characterized by 34 lines. The
tetragonal unit-cell parameters calculated from the
X-ray powder diffraction pattern are equal (within
experimental error) to the most often observed unit-cell
parameters for single-crystalline samples (the average
deviation of the calculated interplanar spacings from
the measured values is 0.003, and the De Wolf figure-
of-merit is 28).
As compared to PtS (PDF 18-972), the X-ray pow-
der diffraction pattern (Fig. 4) and single-crystal X-ray
diffraction patterns for most samples are characterized
by a shift of most of reflections to larger angles. The
X-ray diffraction patterns of some samples are charac-
Table 1. Chemical composition of PtS single crystals
Analysis wt % at % Crystal-chemical formula
Pt Fe S ΣPt Fe S
1 82.506 15.900 98.406 46.05 53.95 Pt0.921S1.079
2 83.815 15.118 98.933 47.70 52.30 Pt0.954S1.046
3 83.875 0.032 15.082 98.989 47.70 0.05 52.25 (Pt0.954Fe0.001)0.955S1.045
4 84.204 14.885 99.090 48.20 51.80 Pt0.964S1.036
5 84.301 0.044 14.828 99.173 48.20 0.10 51.70 (Pt0.964Fe0.002)0.966S1.034
6 84.325 14.813 99.138 48.35 51.65 Pt0.967S1.033
7 84.481 0.031 14.720 99.232 48.50 0.05 51.45 (Pt0.970Fe0.001)0.971S1.029
8 84.251 0.035 14.557 99.372 48.70 0.05 51.25 (Pt0.974Fe0.001)0.975S1.025
9 84.684 0.025 14.456 99.405 49.00 0.05 50.95 (Pt0.980Fe0.001)0.981S1.019
10 84.408 14.394 99.442 49.10 50.90 Pt0.982S1.018
11 85.115 14.341 99.456 49.40 50.60 Pt0.988S1.012
12 85.186 0.027 14.299 99.512 49.45 0.05 50.50 (Pt0.989Fe0.001)0.990S1.010
13 85.287 0.022 14.238 99.547 49.60 0.05 50.35 (Pt0.992Fe0.001)0.993S1.007
14 84.833 14.107 99.669 49.70 50.30 Pt0.994S1.006
15 85.461 14.134 99.596 49.85 50.15 Pt0.997S1.003
16 85.594 14.055 99.649 50.05 49.95 Pt1.001S0.999
17 85.826 13.917 99.742 50.35 49.65 Pt1.007S0.993
18 85.970 13.830 99.800 50.55 49.45 Pt1.011S0.989
19 85.986 13.821 99.807 50.55 49.45 Pt1.011S0.989
20 86.011 13.806 99.817 50.60 49.40 Pt1.012S0.988
21 86.011 13.806 99.817 50.60 49.40 Pt1.012S0.988
22 86.200 13.693 99.893 50.85 49.15 Pt1.017S0.983
23 86.424 13.559 99.983 51.20 48.80 Pt1.024S0.976
24 86.484 13.524 100.008 51.25 48.75 Pt1.025S0.975
25 86.536 13.492 100.028 51.30 48.70 Pt1.026S0.974
26 86.743 13.369 100.112 51.60 48.40 Pt1.032S0.968
27 86.630 13.317 99.947 51.70 48.30 Pt1.034S0.966
28 87.223 13.082 100.305 52.30 47.70 Pt1.046S0.954
29 87.238 13.073 100.311 52.30 47.70 Pt1.046S0.954
30 87.256 13.062 100.318 52.35 47.65 Pt1.047S0.953
31 87.419 12.965 100.384 52.60 47.40 Pt1.052S0.948
32 88.082 12.569 100.651 53.55 46.45 Pt1.071S0.929
33 89.285 11.850 101.135 55.35 44.65 Pt1.107S0.893
34 89.292 11.846 101.138 55.35 44.65 Pt1.107S0.893
Note: The sensitivity of the method with respect to iron is 0.0025 wt %.
CRYSTALLOGRAPHY REPORTS Vol. 53 No. 3 2008
SINGLE-CRYSTALLINE COOPERITE (PtS): CRYSTAL-CHEMICAL CHARACTERIZATION 395
terized by a decrease in the interplanar spacing d100 to
3.446 Å (Fig. 5). An increase in the deficiency of plati-
num in cooperite and the appearance of an iron impu-
rity isomorphously replacing platinum causes a
decrease in all unit-cell parameters (Table 2). An
increase in the intensities of most of reflections, up to
the appearance of the 201 reflection (1.66–1.67 Å),
whose intensity in the theoretical X-ray diffraction pat-
tern is equal to zero, is apparently attributed to the
imperfections of the crystal structure caused by the
deviation from the stoichiometric composition of coo-
perite.
195Pt NMR Spectroscopic Data
In many cases, MAS NMR spectroscopy provides
unique information on the structural and electronic
state of metals in different compounds (see, for exam-
ple, [9–11]). Hence, we applied this method to this
method to the investigation of cooperite. The resulting
195Pt MAS NMR spectrum of single-crystalline cooper-
ite grains obtained by the summation of nine fragments
(recorded with a frequency step of 100 kHz) is pre-
sented in Fig. 6a. The width and shape of the MAS
NMR spectrum provide evidence that the 195Pt chemi-
cal-shift tensor is similar to that corresponding to the
axial symmetry. The anisotropy of the 195Pt chemical
shift is so large that the spectrum contains more than
100 spinning harmonics even at the sample-spinning
frequency of 8000(1) Hz. Because of this, to reveal the
195Pt resonance signal in the center of gravity of the
spectrum, which is characterized by the isotropic chem-
ical shift, we recorded the MAS NMR spectrum using
a continuous swinging of the sample-spinning fre-
quency. In this case, the amplitude of the signal (or sig-
nals) in the center of gravity of the spectrum remains
unchanged, whereas the spinning sidebands are cata-
strophically broadened (Fig. 6b). The above-described
data show that two crystallographically independent
platinum sites in the crystal lattice of cooperite are
structurally equivalent and are characterized by the iso-
tropic chemical shift δ(195Pt) = –1850 ppm (the width of
the resonance signal is 375 Hz).
To determine the principal values of the 195Pt chem-
ical-shift tensor, the static NMR spectrum of a thor-
oughly ground powder of cooperite was recorded in
fragments (Fig. 7). Three singularities corresponding to
δxx = –5920 ± 20 ppm, δyy = –3734 ± 5 ppm, and δzz =
+4023 ± 20 ppm were revealed. In addition, the anisot-
ropy of the 195Pt chemical shift, which was specified as
δaniso = δzz – δiso, and the asymmetry parameter η = 0.37
{η = (δyy – δxx)/(δzz – δiso)}, were calculated from the
experimental data; 195Pt δaniso = 5873 ppm and η = 0.37.
It should be noted that η = 0 corresponds to the axially
symmetric chemical-shift tensor. An increase in η in the
range from 0 to 1 reflects an increase in the contribution
of the orthorhombic component.
Pt(+2)
S(–2)
c
b
a
(a) (b)
0.4
0 35 50 65 80 95 110 125 140 155 170
0
2θ, deg
0.2
0.6
0.8
1.0
I, rel. units
100 002
110
102
112
103
200
201
211
104
203
213
204
310
312
006
106 215
116
304
314
206400
216 410 411
330
332
226 413
420
1.0
0.8
0.6
0.4
0
I, rel. units
0.2
100
002
101
25 30 2θ, deg
Fig. 3. (a) Crystal lattice and (b) the mutual spatial orienta-
tion of the platinum and sulfur polyhedra in cooperite (mod-
els were constructed with the use of the TOPOS-4.0 pro-
gram).
Fig. 4. Experimental X-ray powder diffraction pattern of
cooperite.
Fig. 5. Fragment of the X-ray powder diffraction pattern of
cooperite (the profiles and intensities of simulated reflec-
tions are shown by a dashed line).
396
CRYSTALLOGRAPHY REPORTS Vol. 53 No. 3 2008
ROZHDESTVINA et al.
There is a good probability that the least shielded
direction for the platinum nucleus (the z axis of the
chemical-shift tensor) coincides with the fourfold sym-
metry axis of the square-planar chromophore [PtS4].
Two other directions cannot coincide with the x and y
molecular axes, because the very small difference
(0.0001 Å) in the length of the nonequivalent Pt–S
bonds cannot account for considerable differences in
the degree of electronic shielding. Most likely, these
directions coincide with the bisectors of the S–Pt–S
angles. However, in the case of a more shielded posi-
tion of the platinum nucleus, the axis passes inside the
small-size four-membered metallocycle [Pt2S2]. For the
less shielded position, the axis passes through the
extended eight-membered ring [Pt4S4].
Thoroughly ground cooperite grains give a multi-
component anisotropic ESR spectrum superimposed
onto a broad envelope (Figs. 8a, 8b). The double differ-
entiation (Fig. 8c) allowed us to reveal the correspon-
dence of the spectrum to the axial symmetry (gx = gy < gz),
the presence of quartets of the components of the
hyperfine structure in the parallel and perpendicular
orientations, and the additional absorption line [12, 13]
at high field. The well-resolved quartet structure of
anisotropic ESR spectra is typical of magnetically
dilute copper(II) compounds. The ESR parameters
refined based on the results of the computer simulation
(g|| = 2.358, = 117 Oe, g⊥ = 2.116, = 29 Oe)
are also consistent with interactions between the
unpaired electron (the ground state AO) and
the 63,65Cu nucleus (I = 3/2). However, these results pro-
vide no evidence that copper(II) is included in the crys-
tal lattice of cooperite. The fact is that the square-planar
chromophores [CuS4], for example, in coordination
copper(II) compounds with dithiooxamide and its
dialkyl-substituted derivatives [14], the N,N-dialky-
ldithiocarbamate ligand [15], and the O,O'-dialky-
ldithiophosphate ligand [16], are characterized by sub-
stantially smaller g factors and larger hyperfine-struc-
ture constants (g|| = 2.085, = 164 Oe, g⊥ = 2.024,
ACu
|| ACu
⊥
3dx2y2
–
ACu
||
Table 2. Unit-cell parameters and volume of PtS single crystals
Crystallochemical formula a, Å c, Å c/2aV, Å3
Pt1.012S0.988 3.4710(2) 6.1084(5) 0.88 73.595(5)
Pt1.001S0.999 3.4703(1) 6.1089(5) 0.88 73.569(5)
Pt0.997S1.003 3.4702(3) 6.1089(7) 0.88 73.569(6)
(Pt0.992Fe0.001)0.993S1.007 3.4690(1) 6.1018(5) 0.879 73.431(5)
(Pt0.989Fe0.001)0.990S1.010 3.4686(1) 6.1024(5) 0.88 73.419(6)
Pt0.982S1.018 3.4642(1) 6.0931(7) 0.879 73.125(6)
(Pt0.980Fe0.001)0.981S1.019 3.4637(1) 6.0606(8) 0.875 72.712(7)
(Pt0.974Fe0.001)0.975S1.025 3.4635(2) 6.0562(5) 0.874 72.649(5)
(Pt0.970Fe0.001)0.971S1.029 3.4630(3) 6.0514(7) 0.874 72.573(6)
(Pt0.964Fe0.002)0.966S1.034 3.4634(1) 6.0494(7) 0.873 72.567(6)
(Pt0.954Fe0.001)0.955S1.045 3.4639(1) 6.0398(5) 0.872 72.47(5)
2500 0 –2500 –5000
δ, ppm
(a)
(b)
Fig. 6. (a) Resulting 195Pt MAS NMR spectrum of single-
crystalline grains of cooperite (the upper vertical mark indi-
cates the resonance signal in the center of gravity of the
spectrum). The sample-spinning frequency was 8000(1)
Hz. (b) The spectrum measured with the use of continuous
swinging of the spinning frequency.
4000 3000 2000 1000 –3000 – 4000 –5000 –6000
δ, ppm
Fig. 7. Fragment of 195Pt static NMR spectrum of a coo-
perite powder.
CRYSTALLOGRAPHY REPORTS Vol. 53 No. 3 2008
SINGLE-CRYSTALLINE COOPERITE (PtS): CRYSTAL-CHEMICAL CHARACTERIZATION 397
= 40 Oe; the most typical parameters are given).
The analysis of the ESR data for copper(II) in polyhe-
dra with different compositions and geometric parame-
ters [17] leads to the conclusion that the ESR spectrum
observed for cooperite is determined by copper(II) in
the octahedral environment formed by oxygen atoms.
These data suggest that changes in the hydrothermal
conditions in the course of crystallogenesis of cooperite
were accompanied by adsorption of copper(II) on the
surface as oxides, hydroxides, or hydroxycarbonate
compounds (in the case of the layer-by-layer crystal
growth, which is dominant for minerals).
CONCLUSIONS
The generalized crystal-chemical formula for sin-
gle-crystalline samples of cooperite, which were found
in placers from the Yuna-Dan’sk gold-ore cluster of the
platinum-bearing province in the Sea of Okhotsk region
of the Maœmakansk zone in the Far East, can be written
as Pt1 – xS1 + x (–0.1 ≤ x ≤ +0.1). According to the ESR
data, single-crystalline cooperite samples contain cop-
per(II), which is not included in the crystal lattice of
cooperite. Apparently, the presence of copper(II) in
cooperite, as well as a deficient or excess amount of
platinum, are responsible for the appearance of defor-
mation defects in the structure, which are reflected in
X-ray diffraction patterns. It was demonstrated that
195Pt static and MAS NMR spectroscopy can, in princi-
ple, be used for studying natural platinum minerals.
The principal values of the 195Pt chemical-shift tensor
for cooperite were determined.
ACu
⊥
ACKNOWLEDGMENTS
This study was supported by the Russian Founda-
tion for Basic Research and the Far East Division of the
Russian Academy of Sciences (Program “Far East,”
project no. 06-03-96009) and the Presidium of the Far
East Division of the Russian Academy of Sciences
(project no. 06-III-A-08-339).
A.V. Ivanov acknowledges the support of the Agri-
cola Research Centre at the Luléa University of Tech-
nology (Luléa, Sweden).
REFERENCES
1. V. V. Ivanov, Ecological Geochemistry of Elements:
Handbook in 6 Vols. Vol. 5: Rare d Elements, Ed. by
É. K. Burenkov (Ékologiya, Moscow, 1997) [in Rus-
sian].
2. O. E. Yushko-Zakharova, V. V. Ivanov, L. N. Soboleva,
et al., Handbook of Minerals of Noble Metals (Nedra,
Moscow, 1986) [in Russian].
3. L. P. Plyusnina, G. G. Likhoœdov, and A. I. Khanchuk,
Dokl. Akad. Nauk 405 (1), 105 (2005).
4. L. P. Plyusnina, G. G. Likhoœdov, and I. Ya. Nekrasov,
Dokl. Akad. Nauk 370 (1), 99 (2000).
5. V. G. Moiseenko, V. A. Stepanov, L. V. Éœrish, et al.,
Platinoferous Fractions of the Russian Far East
(Dal’nauka, Vladivostok, 2004) [in Russian].
6. P. P. Safronov and V. G. Moiseenko, Mineral Associa-
tions of Platinoids from Gold-Bearing Placers of the
Zeya-Selemja Area (Priamurie). Geodynamics and Met-
allogeny (Dal’nauka, Vladivostok, 1999), p. 157 [in Rus-
sian].
7. W. Kraus and G. Nolze, J. Appl. Crystallogr. 29 (3), 301
(1996).
8. G. A. Kirakosyan, Koord. Khim. 19 (7), 507 (1993).
9. A. V. Ivanov, A. V. Gerasimenko, O. N. Antzutkin, and
W. Forsling, Inorg. Chim. Acta 358 (9), 2585 (2005).
10. A.-C. Larsson, A. V. Ivanov, K. J. Pike, et al., J. Magn.
Reson. 177 (1), 56 (2005).
11. A. V. Ivanov, A. V. Gerasimenko, A. A. Konzelko, et al.,
Inorg. Chim. Acta 359 (12), 3855 (2006).
12. I. V. Ovchinnikov and V. N. Konstantinov, J. Magn.
Reson. 32, 179 (1978).
13. Ph. H. Rieger, Electron Spin Resonance (Senior
Reporter Symons M.C.R.) (Athenaeum, Newcastle upon
Tyne, 1993), Vol. 13B, p. 178.
14. P. M. Solozhenkin, A. V. Ivanov, and E. V. Rakitina, Zh.
Neorg. Khim. 28 (12), 3081 (1983).
15. A. V. Ivanov and P. M. Solozhenkin, Zh. Neorg. Khim.
35 (6), 1537 (1990).
16. A. V. Ivanov, A.-K. Larsson, N. A. Rodionova, et al., Zh.
Neorg. Khim. 49 (3), 423 (2004).
17. S. A. Al’tshuler and B. M. Kozyrev, Electron Spin Reso-
nance in Compounds of Intermediate-Group Elements
(Nauka, Moscow, 1972) [in Russian].
Translated by T. Safonova
116 Oe
H
262 Oe
H116 Oe
H
DPPH DPPH
DPPH
(a)
(b)
(c) 1
2
Fig. 8. ESR spectra of a cooperite powder. (a) The overall
view. (b) The anisotropic spectrum of copper(II), the first
derivative. (c) The third derivatives; 1, experiment; 2,
model.
