Iridium, Ruthenium and Osmium distribution in Gold Jewellery.
Presented by Ankur Goyal and Pankaj Deshmukh
20th March 2017 LBMA Assaying and Refining Conference
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1.
2
Objectives
Iridium – Ruthenium – Osmium in Gold
Gold or Gold Jewellery may not be as pure or as precious as you think it is!
• Adulteration of Gold by iridium, Ruthenium or
Osmium in domestically refined gold / in hand
made jewellery in the unorganized sector is
rampant in India.
• Fire assay can not address this issue.
• On average, a piece of jewellery / a bar of gold
can contain up to 2% of the adulterant.
• Manufacturers—wholesalers and retailers across
India—are aware of how rampant this notorious
practice is.
3
• Ir, Ru and Os belong to the platinum group of
metals. When mixed with gold they do not alloy
but are dispersed in the gold.
• Cupellation process often quantifies it as GOLD.
• MMTC-PAMP undertook a comprehensive study
on the distribution of Ir, Ru and Os when mixed
in Gold to arrive at optimum sampling pattern to
detect its presence and ascertain the Gold purity.
This study is relevant when we receive scrap at
our PURITY VERIFICATION CENTRE for being
refined.
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Detect distribution of Ir, Ru and Os (PGM) when added to Gold
1
Ir, Ru and Os addition ranging from 0.1% to 0.5% with following combination: Iridium; Iridium and
Ruthenium; Iridium and Osmium
2
Melting in 2 types of induction furnaces with capacity of 500 gm and 2 kg
3
4
Effect on distribution of PGM while melting different quantities of metal ranging from 100 gm to
1600 gm
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2.
5
Properties of Ir, Ru ,Os
Properties of PGMs
Thermal
Conducti
vity
(W/m.K)
Thermal
Expansio
n
(μ.m/mK
@ 25deg
)
Crystal
Structure
Atomic
Mass
Atomic
number
Melting
point
(Deg C)
Boiling
point
(Deg C)
Heat of
fusion
(KJ/mol)
Heat of
vaporisation
(KJ/mol)
Vickers
Hardness
(HV)
Densit
y
(g/cm
3)
Gold
196.96
79
1064.18
2970
12.56
342
19.7 –
22.02
19.3
318
14.2
F.C.C.*
Silver
107.86
47
961.78
2163
11.28
254
25.59
10.49
429
18.9
F.C.C.*
Copper
63.54
29
1084
2562
13.26
300.4
34.98 –
37.62
8.96
401
16.5
F.C.C.*
Iridium
77
77
2446
4130
41.12
564
179.5 224.29
22.56
147
6.4
F.C.C.*
Osmium
190.23
76
3033
5012
31
378
NA
22.59
86.75
5.1
H.C.P**
Ruthenium
101.7
44
2334
4150
38.59
619
NA
12.45
117
6.4
H.C.P**
6
* Face centered Cubic system
** Hexagonal closed packed
Element
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Ir, Ru, Os have a few salient features
Very high melting temperature (>2000 ºC) compared to gold and hence does not melt when gold is melted
(Melting point of gold - 1063 ºC)
Very low solubility in gold and does not go into solid solution (ie alloying) - Floats as black particles on
molten metal surface while melting and can be observed visually.
No reaction with Aqua Regia – remains unreacted during Aqua Regia treatment or during fire assay.
Ir and Os have higher specific gravity than gold, hence temptation to adulterate gold.
7
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Advantages and Disadvantages
Advantages
• The process of Jewellery fabrication by cold
working involves annealing which is to restore
alloy ductility by recrystallization of the workhardened structure.
• Annealing leads to coarse grained structure and
addition of 0.01 to 0.1% Iridium, Ruthenium or
Osmium restricts grain growth resulting into fine
grain structure. The finer the grains better is its
workability and also improves surface quality.
Disadvantages
• Ir, Ru and Os When mixed with gold, do not form
an alloy but are dispersed in the Gold
• On testing by Cupellation process these elements
are found in the final gold cornet but cannot be
quantified so is taken as GOLD
• Its difficult to remove these elements by Chemical
or electrolytic process easily.
• Results in customer not getting accurate value of
Gold.
8
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3.
9
FIRE ASSAY-X-RAY – SEM
a quick overview
Fire Assay
Salient points
Detection
• Key to fire assay is homogeneity in the lot being tested
and drawing a sample that is representative of the
whole LOT.
• For Fire assay sampling, drilling is done at few spots and
then 250 mg of drill is taken for analysis. The probability
of detecting PGM thus gets limited
• Fire assaying is used for the determination of Gold,
Silver and PGM in all types of materials, ranging from
bullion, jewellery and ores to concentrates and
electronic scrap.
• Fire Assay is done at 1150 °C and due to high melting
point of Ir, Ru and Os which is above 2000 C, these PGM
do not mixed with Gold but is dispersed in the Yellow
metal and are available in scattered form as fine
particles.
• This process leaves the precious metal bead on the
cupel, which is weighed accurately to obtain total
precious metal weight. This bead is then treated further
using nitric acid to determine the metals in the bead,
usually silver and gold (gravimetrically), platinum and
palladium (ICP).
10
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Fire Assay
1
2
3
4
5
6
12
11
10
9
8
7
11
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Fire assay gives only the qualitative evaluation
Presence of Ir/Ru/Os in cornets
• By visual inspection of the cornet after the fire
assay process, the presence of Iridium &
Ruthenium may be found as tiny black particles
(as shown in figures of cornets) by skilled Lab
Chemists. To ascertain the exact % of PGM the
cornet has to be dissolved in Aqua regia and the
impurities separated out to arrive at the actual
gold content purity.
12
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XRF - X-ray Fluorescence
XRF is an acronym for x-ray fluorescence, a process whereby electrons are displaced from their atomic
orbital positions, releasing a burst of energy that is characteristic of a specific element. This release of
energy is then registered by the detector in the XRF instrument, which in turn categorizes the energies
by element. The entire fluorescence process occurs in a mille-second.
13
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XRF Spectrometer – Equipment Details
14
Specification
Spectro
Model
XRF SPECTRO MIDEX LD
Measuring distance
0….4.4mm
Detection system
Si-drift detector with Peltier cooling:
Si-drift detector with Peltier cooling
X-ray source
X-ray tube with Mo anode
Micro focus tube with tungsten target &
Beryllium window
Detector position
Upper chamber
Lower chamber
Fischer
XRF FISCHER XAN250
0……10mm(0…..0.4in)
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X-ray Fluorescence Spectrometry (XRF)
Salient features
• Well suited technique for determination of trace
elements as testing is carried out directly on the solid
sample and not by acid digestion.
• The precision of the XRF technique is normally very
high and is demonstrated by evaluation of replicate
results.
• Accuracy on the other hand depends heavily on two
factors: the attenuation-enhancement correction
procedure used to correct matrix effects caused by
concomitant elements, and reference standards used in
calibration procedures.
• Laboratories analyzing samples with variable matrices
require a high skilled professional along with proficiency
in the XRF technique to produce accurate data.
15
Detection of PGM
• XRF Spectrometer can be used to check/detect the
presence of Iridium and Ruthenium impurities in Gold
Alloys. The resolution of Semi-conductor Detector is 4
times (approx.) of the Gas-filled Proportional counter,
and is thus able to resolve /separate the peaks of
interest.
• XRF gives the purity at each spot, thereby increasing
the probability of detection of these PGM which is very
unevenly distributed in the ingot/sample.
• XRF usage is significant to detect lack of homogeneity,
and is an invaluable tool for identifying locations for
drawing samples from hand-made jewellery
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XRF
X-ray Fluorescence Spectrometry (XRF)
• XRF gives an accurate percentage of PGM with the
tolerance level of +/- 0.1%
• The Gold, Iridium, Silver & Ru spectra using
proportional counter detector and Silicon PIN Detector
(SiPIN) are shown in the figures alongside.
16
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Samples for XRF
Analysis
Points For
XRF
Flat Button
Round Ingot
Ingot
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Scanning Electron Microscopy
Salient features
• SEM uses a focused beam of high-energy electrons
to generate a variety of signals at the surface of
solid specimens.
• The signals that derive from electron-sample
interactions reveal information about the sample
including external morphology (texture), chemical
composition, and crystalline structure and
orientation of materials making up the sample.
• In most applications, data are collected over a
selected area of the surface of the sample, and a 2dimensional image is generated that displays spatial
variations in these properties.
• Areas ranging from approximately 1 cm to 5 microns
in width can be imaged in a scanning mode using
conventional SEM techniques
18
ZEISS EVO Series Scanning Electron Microscope EVO 50
and EVO 18
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Scanning Electron Microscopy
Salient features
• The ZEISS EVO 50 is a versatile analytical microscope with a large
specimen chamber and can handle specimens at the analytical
working distance of 8.5mm owing to a combination of the
inclined detectors and the sharp conical objective lens.
Resolution
2.0nm@ 30kV (SE with LaB6 option )
Acceleration Voltage
0.2 to 30 kV
Magnification
5x to 1,000,000x
• Microstructures at SEM can be analyzed for its elemental
composition in more detail using EDX system.
Field of View
6 mm at the Analytical Working Distance
(AWD)
• This is a non-destructive analysis and the elements and their
concentration in the sample can be determined reasonably
accurately.
X-ray Analysis
8.5 mm AWD and 35° take-off angle
Available Detectors
• SE in HV - Everhart-Thornley
• SE in VPSE
• BSD in all modes - quadrant
semiconductor diode
• The class leading X-ray geometry allows for the addition of an EDS
detector.
ENERGY DISPERSIVE X-RAY MICROANALYSIS :
• SEMCF has RONTEC’s EDX system Model QuanTax 200 which is
based on the SDD technology and provides an energy resolution
of 127 eV at Mn K alpha.
19
Essential Specification: EVO 50:
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Samples for SEM
Top
0 - Centre
1 - Near centre
2 - Between centre and
circumference
3 - Close to
circumference
Cross
section
Bottom
Top Surface
20
Cross Section
Bottom Surface
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4.
21
Various trials to determine the
presence of Ru, Ir and Os
using XRF as testing method
Samples for XRF
Analysis
Points For
XRF
Flat Button
Round Ingot
Ingot
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Trials with Iridium in 500 gms Shapet Furnace – Sample wt 100 gms
Element/Position
Top
Centre
Bottom
Au (89.5%)
Ir (0.5%)
Au (89.5%)
Ir (0.4%)
Au (89.5%)
Ir (0.3%)
Au (89.5%)
Ir (0.2%)
Au (89.5%)
Ir (0.1%)
89.75
89.45
89.61
89.46
89.62
89.79
89.23
89.42
89.52
89.43
89.11
89.48
88.86
89.52
88.94
88.99
89.39
89.33
89.5
89.41
89.25
89.09
89.31
89.45
89.41
89.45
89.54
89.37
89.48
89.11
0.043
0.113
0.220
0.044
< 0.051
< 0.051
0.347
0.104
0.041
0.032
0.514
< 0.051
0.882
0.021
0.749
0.632
0.234
0.260
< 0.051
< 0.051
0.124
0.414
0.198
0.104
< 0.051
< 0.051
< 0.051
0.240
0.094
0.462
89.42
89.48
89.63
89.43
89.58
89.51
89.73
89.5
89.39
89.53
89.59
89.47
89.47
89.19
89.17
89.04
88.98
88.48
89.6
89.21
89.23
89.4
88.93
89.37
89.39
89.04
89.42
89.41
89.29
89.05
0.050
0.047
< 0.051
0.038
0.045
0.048
< 0.051
< 0.051
0.030
< 0.051
< 0.051
< 0.051
< 0.051
0.282
0.216
0.503
0.249
0.906
0.028
0.277
0.285
0.166
0.580
0.084
0.176
0.466
0.192
0.170
0.211
0.409
89.6
89.79
89.44
89.57
89.68
89.92
89.8
89.66
89.75
89.52
89.59
89.48
89.37
89.5
88.83
89.3
88.54
89.35
89.36
89.29
89.47
89.44
89.57
89.45
89.38
89.34
89.49
89.48
89.11
89.39
< 0.051
0.024
0.048
0.036
0.040
< 0.051
0.041
< 0.051
< 0.051
< 0.051
< 0.051
< 0.051
0.040
< 0.051
0.913
< 0.051
0.868
< 0.051
0.069
0.121
< 0.051
< 0.051
< 0.051
0.037
0.054
0.211
< 0.051
< 0.051
0.397
0.092
89.45
89.56
89.55
89.33
89.59
89.71
90.01
89.53
89.51
89.42
89.48
89.45
89.37
89.36
89.3
89.18
89.76
89.31
89.32
89.58
89.37
89.53
89.54
89.53
89.41
89.52
89.46
89.34
89.81
89.84
0.026
< 0.051
< 0.051
< 0.051
< 0.051
< 0.051
< 0.051
< 0.051
< 0.051
0.043
< 0.051
< 0.051
0.189
0.137
0.054
0.180
< 0.051
0.170
0.068
< 0.051
0.179
< 0.051
0.094
0.089
0.148
0.060
< 0.051
0.118
< 0.051
< 0.051
89.47
89.68
89.72
89.49
89.74
89.83
89.88
89.5
89.51
89.33
89.35
89.48
89.46
89.49
88.68
89.41
88.68
89.09
89.5
89.51
89.55
89.42
89.23
89.51
89.59
89.52
89.39
89.44
89.43
88.7
< 0.051
< 0.051
< 0.051
< 0.051
< 0.016
< 0.016
< 0.051
< 0.051
< 0.051
< 0.017
< 0.051
< 0.051
0.055
0.032
0.537
< 0.051
0.780
0.123
< 0.051
< 0.051
< 0.051
0.127
0.106
< 0.051
< 0.051
< 0.051
< 0.051
< 0.051
< 0.051
0.617
Balance - Silver (5%) and Copper (5%)
23
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Trials with Iridium in 2 Kg Inductotherm Furnace
Bar
Element/Position
Top
Centre
Bottom
1st Bar
(Sample Weight-600 gms)
2nd Bar
(Sample weight-392 gms)
3rd Bar
(Sample weight-508 gms)
Au (80%)
Ir (0.3%)
Ru (0.05%)
Au (80%)
Ir (0.3%)
Ru (0.05%)
Au (80%)
Ir (0.3%)
Ru (0.05%)
79.56
0.0893
< 0.030
79.36
< 0.051
< 0.030
79.3
< 0.051
< 0.030
79.29
< 0.051
< 0.030
79.55
< 0.051
< 0.030
79.14
< 0.051
< 0.030
79.09
0.0767
< 0.030
79.45
< 0.051
< 0.030
79.47
0.105
< 0.030
79.31
0.335
< 0.030
79.09
< 0.051
< 0.030
79.7
0.183
< 0.030
79.53
0.184
< 0.030
79.61
0.1339
< 0.030
79.75
0.435
< 0.030
79.2
0.597
< 0.027
79.75
< 0.019
< 0.030
79.6
0.216
< 0.030
79.67
0.350
< 0.030
79.82
0.252
< 0.030
79.7
0.137
< 0.030
79.67
0.442
< 0.030
79.48
0.317
< 0.030
79.71
0.107
< 0.030
79.39
0.475
< 0.030
79.07
0.870
0.104
79.74
0.064
< 0.030
Balance - Silver (6.5%) and Copper (13.15%)
24
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Trial with Iridium
Gold with addition of Iridium (at a range of 0.1 to 0.5% iridium) in
500 gm furnace with 100 gm metal
25
Gold with addition of Iridium (0.3% ONLY) in 2 kg furnace and
with 100gm, 200 gm and 1600 gm metal
Furnace-1
Furnace-3
Capacity:
500 g
Capacity:
2000 g
Frequency:
Medium
Frequency:
Medium
Power
consumption:
4.5 KW (max)
Power
consumption:
5 KW
Temperature:
1150 °C
Temperature:
1150 °C
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Observation
•
With only Iridium the distribution pattern is from center to bottom.
However, in all cases, the range of detection is seen to vary without any
predictable pattern and deviating from the actual addition.
•
A qualitative vrs quantitative comparison shows that it is relatively easier to
predict the location with more reliability than the quantity.
Inference : The rational approach to minimize the chances of error in detection of Iridium in
karat gold is to draw a sampling plan spreading predominantly at center and bottom at
multiple location.
26
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Trials With Iridium & Ruthenium in 500 gms Shapet furnace
Sample Weight - 100 gms (Ref4)
Element/Position
Top
Centre
Bottom
27
Sample Weight - 1000 gms (Ref4)
Au (86.1%)
Ag (5%)
Cu (8%)
Ir (0.5%)
Ru (0.4%)
Au (89.1%)
Ag (5%)
Cu (5%)
Ir (0.3%)
Ru (0.6%)
82.34
4.939
10.6
0.538
1.583
84.89
5.02
9.942
0.1366
< 0.030
83.05
4.841
10.44
0.605
1.057
84.43
5.012
9.898
0.1941
0.455
81.82
4.749
10.07
0.769
2.592
85.24
5.006
9.64
0.1177
< 0.030
81.85
4.859
10.77
0.496
2.021
85.17
5.098
9.615
0.0719
0.0406
78.96
4.779
9.462
1.148
5.643
85.44
5.093
9.453
< 0.051
< 0.030
81.74
4.67
9.788
0.854
2.933
80.52
4.777
9.894
1.429
3.37
79.32
4.749
9.741
1.328
4.851
84.95
5
9.852
0.1949
< 0.030
82.73
4.875
9.994
0.446
1.945
83.15
4.938
10.02
0.501
1.377
Element/Position
Top
81.1
4.842
9.811
0.637
3.602
85.14
5.06
9.715
0.0763
< 0.030
83.93
4.952
10.21
0.421
0.462
84.28
4.902
10.07
0.447
0.298
84.06
4.847
10.08
0.451
0.545
84.22
4.938
9.951
0.505
0.377
Centre
84.8
4.926
10.21
0.0529
< 0.030
84.76
4.978
10.25
< 0.051
< 0.030
84.72
4.953
10.32
< 0.051
< 0.030
84.84
5.007
10.15
< 0.051
< 0.030
84.82
4.934
10.23
< 0.051
< 0.030
84.87
4.919
10.21
< 0.051
< 0.030
84.84
4.852
10.23
0.0743
< 0.030
84.5
5.007
10.33
0.1477
< 0.030
84.73
4.906
10.35
< 0.051
< 0.030
84.13
4.882
10.93
0.0474
< 0.030
84.18
4.891
10.93
< 0.051
< 0.030
84.63
5.037
10.32
< 0.051
< 0.030
84.85
4.944
10.2
< 0.051
< 0.030
84.62
5.077
10.29
< 0.051
< 0.030
84.84
5
10.15
< 0.051
< 0.030
84.8
4.998
10.19
< 0.051
< 0.030
84.89
4.826
10.27
< 0.051
< 0.030
84.76
4.992
10.24
< 0.051
< 0.030
Bottom
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Trials With Iridium & Ruthenium in 2 kgs Inductotherm furnace
Sample Weight - 200 gms (Ref10)
Element/Position
Top
Center
Bottom
Sample Weight - 1000 gms (Ref12)
Au (87.1%)
Ir (0.3%)
86.97
0.1025
87.32
0.0622
84.18
0.512
87.43
Ru (0.6%)
Au (87.1%)
Ir (0.3%)
Ru (0.6%)
0.277
83.17
0.785
3.599
< 0.030
86.49
0.137
1.064
2.552
87.25
0.138
0.192
0.0596
< 0.030
85.55
0.368
1.639
87.23
0.1736
0.347
86.83
0.070
0.100
86.03
0.408
0.85
86.82
0.118
0.442
87.01
< 0.018
0.1602
83.24
2.099
2.453
Element/Position
Top
86.8
0.1995
0.447
87.25
0.070
0.082
86.46
0.239
0.746
86.71
0.200
0.614
86.05
0.2068
0.518
84.67
2.670
0.806
86.51
0.1543
0.261
82.46
2.187
3.814
86.89
< 0.051
< 0.030
84.85
0.426
2.929
86.9
0.0219
< 0.030
87.76
< 0.051
< 0.030
Center
86.91
< 0.051
< 0.030
87.66
< 0.051
< 0.030
86.78
0.0307
< 0.030
87.44
0.074
< 0.030
86.88
< 0.051
< 0.030
87.82
< 0.051
< 0.030
86.99
< 0.051
< 0.030
87.54
< 0.051
< 0.030
86.82
0.0482
< 0.030
87.55
0.030
< 0.030
86.87
< 0.051
< 0.030
87.68
< 0.051
< 0.030
86.95
< 0.051
< 0.030
87.56
< 0.051
< 0.030
Bottom
Balance - Silver (5%) and Copper (7%)
28
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Trials With Iridium & Ruthenium
Gold with Iridium (addition ranging 0.3 to 0.5%) and Ruthenium
(addition ranging 0.4 to 0.6%) in 500 gm furnace with 100, 200,
300 and 500 g lot. Using Furnace 1
29
Gold with Iridium (0.3%) and Ruthenium (0.05% -0.6%) in 2 kg
furnace and 200gm, 300gm and 1000 gm lot Using Furnace 3
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Observation
•
With addition of Ruthenium, the distribution seems to reverse in comparison
to previous case when only Iridium was added. In this case, ruthenium being
lighter, is not allowing Iridium to settle towards bottom..
•
A qualitative vrs quantitative comparison shows that it is relatively easier to
predict the location with more reliability than the quantity.
Inference : The rational approach to minimize the chances of error in detection of Ruthenium
in karat gold is to draw a sampling plan spreading predominantly at top to centre at multiple
location.
30
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Trials With Iridium & Osmium in 500 gm Shapet Furnace
Sample weight - 300 gms (Ref 4)
Element/Position Au (89.3%) Ag (5%)
Top
Centre
Bottom
31
89.5
89.47
89.23
89.48
89.49
89.37
89.11
89.45
87.87
89.47
88.69
88.58
88.43
89.53
89.49
5.296
5.366
5.459
5.279
5.346
5.419
5.391
5.393
5.368
5.42
5.358
5.349
5.318
5.381
5.456
Sample weight - 300 gms (Ref 17)
Cu (5%)
Ir (0.3%)
5.195
5.152
5.213
5.226
5.161
5.199
5.085
5.115
5.063
5.097
5.15
5.016
5.141
5.077
5.046
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
0.2085
0.0247
0.76
< 0.010
0.1972
0.0709
0.478
< 0.010
< 0.010
Os
(0.4%)
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
0.202
< 0.049
0.934
< 0.010
0.597
0.977
0.618
< 0.010
< 0.010
Element
Top
Centre
Bottom
Au (89.3%) Ag (5%) Cu (5%) Ir (0.3%) Os (0.4%)
89.11
88.74
89.57
88.83
88.65
88.99
87.01
88.45
89.13
89.38
89.27
89.07
89.24
89.47
89.55
5.305
5.463
5.381
5.336
5.406
5.304
5.351
5.441
5.472
5.429
5.461
5.475
5.417
5.346
5.321
5.57
5.646
5.045
5.667
5.764
5.604
5.148
5.19
5.175
5.178
5.257
5.441
5.314
5.182
5.12
< 0.010
0.025
< 0.010
< 0.010
< 0.012
< 0.010
0.4091
0.446
0.0887
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
0.0613
< 0.010
< 0.010
< 0.050
0.0503
2.048
0.467
0.125
< 0.010
< 0.010
< 0.010
< 0.048
< 0.010
< 0.048
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Trials With Iridium & Osmium in 2 kg Induction furnace
Sample weight - 200 gms (Ref 7)
Sample Weight - 100 gms (Ref 14)
Element/Position Au (89.3%) Ag (5%) Cu (5%) Ir (0.3%) Os (0.4%)
Top
Centre
Bottom
32
89.23
89.35
89.19
89.07
89.16
89.21
89.09
89.19
89.12
89.65
89.47
89.55
89.46
89.54
89.6
5.448
5.466
5.364
5.406
5.421
5.399
5.416
5.308
5.374
5.447
5.494
5.447
5.471
5.287
5.402
5.229
5.176
5.35
5.16
5.363
5.265
5.076
5.066
5.074
4.892
5.018
4.992
5.015
5.165
4.988
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
0.2081
0.1931
0.386
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.049
< 0.010
< 0.010
< 0.010
0.205
0.243
< 0.048
< 0.010
< 0.047
< 0.010
< 0.047
< 0.047
< 0.010
Element/Position Au (89.3%) Ag (5%) Cu (5%) Ir (0.3%) Os (0.4%)
Top
Centre
Bottom
89.22
89.19
89.2
88.91
88.78
88.79
88.99
88.72
88.51
89.27
89.41
89.22
89.39
89.33
89.4
5.329
5.552
5.464
5.569
5.467
5.459
5.422
5.429
5.386
5.446
5.438
5.564
5.332
5.525
5.454
5.376
5.244
5.262
4.747
5.399
5.636
5.203
5.18
5.224
5.253
5.144
5.206
5.273
5.14
5.139
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
0.133
0.45
0.0894
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
< 0.010
0.246
0.21
0.776
< 0.010
< 0.010
< 0.010
< 0.048
< 0.010
< 0.010
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Trials With Iridium & Osmium
Gold with Iridium (0.3%) and Osmium (0.4%) in 500 g furnace for
100, 200 and 300 g lot. Using Furnace 1
33
Gold with Iridium (0.3%) and Osmium (0.4%) in 2 kg furnace for
100, 200 and 300 g lot. Using Furnace 3
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Observation
•
Osmium and Iridium being heavy is predominantly found more at center and
also at bottom.
•
The possibility of detecting Iridium and Osmium quantity is still very unpredictable.
•
Osmium tends to form Osmium tetraoxide above 400 C and is highly volatile.
Inference : Predominantly detection at centre and bottom.
34
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5.
35
Scanning Electron Microscope
XRF Analysis
PGM ANALYSIS SAMPLES FOR IIT (DELHI)
Au
Ag
Cu
Ir
Os
Ru
%
%
%
%
%
%
1
89.50
3.00
7.00
0.50
2
87.50
4.00
8.00
3
88.00
5.50
6.00
4
87.00
4.00
7.00
Sample No.
36
19.35
0.50
1.00
Sample wt.
0.50
19.51
0.50
19.56
0.50
19.53
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Samples for SEM
Top
0 - Centre
1 - Near centre
2 - Between centre and
circumference
3 - Close to
circumference
Cross
section
Bottom
Top Surface
37
Cross Section
Bottom Surface
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Gold – Iridium System
Centre
Circumference
Distribution of Iridium
Top
Top
Locations
Loc 0
Loc 1
Loc 2
Loc 3
% Composition
1.94
2.36
3.84
4.66
Cross
section
Bottom
Cross section
Locations
Loc 0
Loc 1
Loc 2
% Composition
3.01
1.68
2.245
Bottom
Locations
Loc 0
Loc 1
Loc 2
% Composition
2.535
1.64
1.84
38
Iridium moves towards the periphery of the
mold during pouring, but being much
heavier tends to migrate towards the
bottom
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SEM Imaging of Gold Iridium System
Centre
intermediate
Circumference
Top Surface
Cross section
Bottom Surface
39
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SEM Imaging of Gold Iridium System
Centre
Bottom Surface
Distributed uniformly but
seems to form elongated
clusters.
40
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Gold – Ruthenium System
Centre
Circumference
Distribution of Ruthenium
Top
Location
Loc 0
Loc 1
Loc 2
Loc 3
% Composition
15.1
1.94
0.25
1.13
Top
Centre
Bottom
Cross section
Location
Loc 0
Loc 1
Loc 2
% Composition
1.03
0.05
0.945
Ruthenium being lighter tends to float
and predominantly moves to the top
Bottom
Location
Loc 0
Loc 1
Loc 2
% Composition
0
0.7
1.215
41
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SEM Imaging of Gold Ruthenium System
Centre
intermediate
Circumference
Top Surface
Cross section
Bottom Surface
42
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SEM Imaging of Gold Ruthenium System
Centre
Top Surface
Dispersed in irregular
manner, showing big lumps
or clusters .
43
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Gold – Osmium System
Centre
Circumference
Distribution of Osmium
Top
Location
Loc 0
% Composition
Loc 1
4.02
3.85
Loc 2
Loc 3
3.05
Top
3.27
Centre
Bottom
Cross section
Location
Loc 0
Loc 1
Loc 2
% Composition
3.48
3.17
2.915
Bottom
44
Location
Loc 0
Loc 1
Loc 2
% Composition
3.455
3.05
3.425
During pouring, Os aided with it’s high density
propels it to drop down without much lateral
movement It is pre-dominantly present at
bottom and is more uniform in shape.
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SEM Imaging of Gold Osmium System
Centre
intermediate
Circumference
Top Surface
Cross section
Bottom Surface
45
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SEM Imaging of Gold Osmium System
Bottom Surface
intermediate
Cluster formation is least;
more dense, round spots.
46
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Gold – Iridium-Osmium-Ruthenium System
Osmium
Locations
% Composition
% Composition
% Composition
Locations
% Composition
% Composition
% Composition
Locations
% Composition
% Composition
% Composition
47
Top
Iridium
Distribution in multi-component system
Ruthenium
Top
Os
Loc 0
3.78
Loc 1
3.58
Loc 2
3.83
Loc 3
3.78
Ir
1.5
2.23
2.58
3.32
Ru
0.41
0.62
0.72
0.73
Cross section
Os
Loc 0
3.04
Loc 1
3.69
Loc 2
4.115
Ir
2.41
2.41
2.14
Ru
0
0.55
0.8
Bottom
Os
Loc 0
2.28
Loc 1
2.22
Loc 2
2.71
Ir
0.94
2.08
2.085
Ru
2.67
0.63
0.005
Centre
Bottom
Ir is present at periphery at top
and settles at centre in bottom
Ru is present at periphery at top
and settles at centre in bottom
Os seems to be present at all 3
locations
An MKS PAMP GROUP Company
SEM Imaging of Iridium in the multi-component system
Centre
intermediate
Circumference
Top Surface
Cross section
Bottom Surface
48
An MKS PAMP GROUP Company
SEM Imaging of Ruthenium in the multi-component system
Centre
intermediate
Circumference
Top Surface
Cross section
Bottom Surface
49
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SEM Imaging of Osmium in the multi-component system
Centre
intermediate
Circumference
Top Surface
Cross section
Bottom Surface
50
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6.
51
Inferences
XRF spectrometer is the need of the hour
 Using XRF by a suitable sampling procedure its possible to detect the
presence of Ir, Ru and Os, though to accurately predict the percentage of
these elements is still difficult as its dispersed in the metal and do not form a
solid solution
 In Fire Assay Method its difficult to have Qualitatively or quantitatively detect
the presence of Iridium, Ruthenium and Osmium . The possibility of the
catching these elements in sampling of Fire assay is very low.
 An experienced and skilled assayer only can really identify the presence of
these elements in cupellation or on beads or on cornet! But even after this,
its tedious job to find out the concentration of these elements in sample by
using chemical digestion and spectroscopic analysis!
 When presence detected by XRF, aqua regia process must precede fire assay.
52
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Trend analysis and data interpretation of samples tested
Only Iridium
Iridium-Ruthenium
Iridium-Osmium
• When only Iridium is present in sample,
the trend for qualitative analysis of iridium
is in ascending order from Center towards
Bottom side.
• When samples contains only iridium, the
no. of analysis spots at bottom side must
be increased to enhance detection
probability.
• When Iridium-Ruthenium is present in
sample, then the trend for qualitative
analysis of iridium is in ascending order
from Center towards Top side.
• When samples contains
iridium/ruthenium, the no of spots of
analysis at Top side must be increased to
enhance detection probability.
• When Iridium-Osmium is present in
sample, then the trend for qualitative
analysis of iridium-osmium is in ascending
order from bottom towards Center side.
• When samples contains iridium-osmium,
the no of spots of analysis at Center side
must be increased to enhance detection
probability
High value detection predominantly towards
Bottom and center.
53
TOP
CENTER
BOTTOM
BOTTOM
TOP
CENTER
Center
Analysis
Points
Center
Bottom
Analysis
Points
High value detection predominantly towards
Top and center.
TOP
CENTER
BOTTOM
Top
Bottom
Center
Analysis
Points
High value detection predominantly towards
Center and bottom.
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Research team
Conceptualization of the paper
Ankur Goyal : Metallurgist
Debasish Bhattacharjee : Metallurgist
Pankaj Deshmukh : Analytical chemistry
Melting and Analysis by XRF
Jaideep : Chemist
Analysis by SEM
Prof Jayant Jain : Indian Institute of Technology Delhi
Compilation of the data
Praveen Kumar – Chemical Engineer
Special Thanks to Mr Rajesh Khosla to have guided us for this Research
54
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THANK YOU
27