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An MKS PAMP GROUP Company

Iridium, Ruthenium and Osmium distribution in Gold Jewellery. Presented by Ankur Goyal and Pankaj Deshmukh

20th March 2017 LBMA Assaying and Refining Conference

Objectives 1.

2


Iridium – Ruthenium – Osmium in Gold

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• 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.

Gold or Gold Jewellery may not be as pure or as precious as you think it is!

• 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.

• 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.

• 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.


Detect distribution of Ir, Ru and Os (PGM) when added to Gold

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Ir, Ru and Os addition ranging from 0.1% to 0.5% with following combination: Iridium; Iridium and Ruthenium; Iridium and Osmium

Effect on distribution of PGM while melting different quantities of metal ranging from 100 gm to 1600 gm

Melting in 2 types of induction furnaces with capacity of 500 gm and 2 kg

1

3

2

Properties of Ir, Ru ,Os 2.

5


Properties of PGMs

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Element 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)

Density

(g/cm3)

Thermal Conducti

vity (W/m.K)

Thermal Expansio

n (μ.m/mK @ 25deg

)

Crystal Structure

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**

* Face centered Cubic system ** Hexagonal closed packed


Ir, Ru, Os have a few salient features

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Very high melting temperature (>2000 ºC) compared to gold and hence does not melt when gold is melted (Melting point of gold - 1063 ºC)

Ir and Os have higher specific gravity than gold, hence temptation to adulterate gold.

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.


Advantages and Disadvantages

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• The process of Jewellery fabrication by cold working involves annealing which is to restore alloy ductility by recrystallization of the work-hardened 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.

• 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.

Disadvantages Advantages

FIRE ASSAY-X-RAY – SEM a quick overview 3.

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Fire Assay

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• Key to fire assay is homogeneity in the lot being tested and drawing a sample that is representative of the whole LOT.

• 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.

• 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).

Salient points

• 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 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.

Detection


Fire Assay

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1 2 3 4 5 6

7 8 9 10 11 12


Fire assay gives only the qualitative evaluation

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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.


XRF - X-ray Fluorescence

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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.


XRF Spectrometer – Equipment Details

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Specification Spectro Fischer

Model XRF SPECTRO MIDEX LD XRF FISCHER XAN250

Measuring distance 0….4.4mm 0……10mm(0…..0.4in)

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


X-ray Fluorescence Spectrometry (XRF)

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• 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.

Salient features

• 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

Detection of PGM


XRF

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• 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.

X-ray Fluorescence Spectrometry (XRF)


Round Ingot Flat Button

Ingot

Analysis Points For

XRF

Samples for XRF


Scanning Electron Microscopy

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• 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 2-dimensional 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

Salient features

ZEISS EVO Series Scanning Electron Microscope EVO 50 and EVO 18


Scanning Electron Microscopy

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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.

• The class leading X-ray geometry allows for the addition of an EDS detector.

ENERGY DISPERSIVE X-RAY MICROANALYSIS :

• Microstructures at SEM can be analyzed for its elemental composition in more detail using EDX system.

• This is a non-destructive analysis and the elements and their concentration in the sample can be determined reasonably accurately.

• 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.

Essential Specification: EVO 50:

Resolution 2.0nm@ 30kV (SE with LaB6 option )

Acceleration Voltage 0.2 to 30 kV

Magnification 5x to 1,000,000x

Field of View 6 mm at the Analytical Working Distance (AWD)

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

An MKS PAMP GROUP Company 20

Samples for SEM

Top Surface Bottom Surface Cross Section

Top

Cross section

Bottom

0 - Centre 1 - Near centre 2 - Between centre and circumference 3 - Close to circumference

Various trials to determine the presence of Ru, Ir and Os using XRF as testing method

4.

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Round Ingot Flat Button

Ingot

Analysis Points For

XRF

Samples for XRF


Trials with Iridium in 500 gms Shapet Furnace – Sample wt 100 gms

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Element/Position 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%)

Top

89.75 0.043

89.42 0.050

89.6 < 0.051

89.45 0.026

89.47 < 0.051 89.45 0.113 89.48 0.047 89.79 0.024 89.56 < 0.051 89.68 < 0.051 89.61 0.220 89.63 < 0.051 89.44 0.048 89.55 < 0.051 89.72 < 0.051 89.46 0.044 89.43 0.038 89.57 0.036 89.33 < 0.051 89.49 < 0.051 89.62 < 0.051 89.58 0.045 89.68 0.040 89.59 < 0.051 89.74 < 0.016 89.79 < 0.051 89.51 0.048 89.92 < 0.051 89.71 < 0.051 89.83 < 0.016 89.23 0.347 89.73 < 0.051 89.8 0.041 90.01 < 0.051 89.88 < 0.051 89.42 0.104 89.5 < 0.051 89.66 < 0.051 89.53 < 0.051 89.5 < 0.051 89.52 0.041 89.39 0.030 89.75 < 0.051 89.51 < 0.051 89.51 < 0.051 89.43 0.032 89.53 < 0.051 89.52 < 0.051 89.42 0.043 89.33 < 0.017 89.11 0.514 89.59 < 0.051 89.59 < 0.051 89.48 < 0.051 89.35 < 0.051 89.48 < 0.051 89.47 < 0.051 89.48 < 0.051 89.45 < 0.051 89.48 < 0.051 88.86 0.882 89.47 < 0.051 89.37 0.040 89.37 0.189 89.46 0.055 89.52 0.021 89.19 0.282 89.5 < 0.051 89.36 0.137 89.49 0.032

Centre 88.94 0.749

89.17 0.216

88.83 0.913

89.3 0.054

88.68 0.537 88.99 0.632 89.04 0.503 89.3 < 0.051 89.18 0.180 89.41 < 0.051 89.39 0.234 88.98 0.249 88.54 0.868 89.76 < 0.051 88.68 0.780 89.33 0.260 88.48 0.906 89.35 < 0.051 89.31 0.170 89.09 0.123

Bottom

89.5 < 0.051

89.6 0.028

89.36 0.069

89.32 0.068

89.5 < 0.051 89.41 < 0.051 89.21 0.277 89.29 0.121 89.58 < 0.051 89.51 < 0.051 89.25 0.124 89.23 0.285 89.47 < 0.051 89.37 0.179 89.55 < 0.051 89.09 0.414 89.4 0.166 89.44 < 0.051 89.53 < 0.051 89.42 0.127 89.31 0.198 88.93 0.580 89.57 < 0.051 89.54 0.094 89.23 0.106 89.45 0.104 89.37 0.084 89.45 0.037 89.53 0.089 89.51 < 0.051 89.41 < 0.051 89.39 0.176 89.38 0.054 89.41 0.148 89.59 < 0.051 89.45 < 0.051 89.04 0.466 89.34 0.211 89.52 0.060 89.52 < 0.051 89.54 < 0.051 89.42 0.192 89.49 < 0.051 89.46 < 0.051 89.39 < 0.051 89.37 0.240 89.41 0.170 89.48 < 0.051 89.34 0.118 89.44 < 0.051 89.48 0.094 89.29 0.211 89.11 0.397 89.81 < 0.051 89.43 < 0.051 89.11 0.462 89.05 0.409 89.39 0.092 89.84 < 0.051 88.7 0.617

Balance - Silver (5%) and Copper (5%)


Trials with Iridium in 2 Kg Inductotherm Furnace

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Bar 1st Bar (Sample Weight-600 gms) 2nd Bar

(Sample weight-392 gms) 3rd Bar (Sample weight-508 gms)

Element/Position Au (80%) Ir (0.3%) Ru (0.05%) Au (80%) Ir (0.3%) Ru (0.05%) Au (80%) Ir (0.3%) Ru (0.05%)

Top

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

Centre

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

Bottom

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%)


Trial with Iridium

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Gold with addition of Iridium (at a range of 0.1 to 0.5% iridium) in 500 gm furnace with 100 gm metal

Furnace-1

Capacity: 500 g Frequency: Medium

Power consumption: 4.5 KW (max)

Temperature: 1150 °C

Gold with addition of Iridium (0.3% ONLY) in 2 kg furnace and with 100gm, 200 gm and 1600 gm metal

Furnace-3

Capacity: 2000 g Frequency: Medium

Power consumption: 5 KW

Temperature: 1150 °C


Observation

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• 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.


Trials With Iridium & Ruthenium in 500 gms Shapet furnace

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Sample Weight - 100 gms (Ref4) Sample Weight - 1000 gms (Ref4)

Element/Position Au (86.1%) Ag (5%) Cu (8%) Ir (0.5%) Ru (0.4%) Element/Position Au (89.1%) Ag (5%) Cu (5%) Ir (0.3%) Ru (0.6%)

Top

82.34 4.939 10.6 0.538 1.583

Top

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

81.1 4.842 9.811 0.637 3.602 85.14 5.06 9.715 0.0763 < 0.030

Centre 83.93 4.952 10.21 0.421 0.462

Centre 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

Bottom

84.8 4.926 10.21 0.0529 < 0.030

Bottom

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


Trials With Iridium & Ruthenium in 2 kgs Inductotherm furnace

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Sample Weight - 200 gms (Ref10) Sample Weight - 1000 gms (Ref12)

Element/Position Au (87.1%) Ir (0.3%) Ru (0.6%) Element/Position Au (87.1%) Ir (0.3%) Ru (0.6%)

Top

86.97 0.1025 0.277

Top

83.17 0.785 3.599 87.32 0.0622 < 0.030 86.49 0.137 1.064 84.18 0.512 2.552 87.25 0.138 0.192 87.43 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 86.8 0.1995 0.447 87.25 0.070 0.082

86.46 0.239 0.746 86.71 0.200 0.614

Center 86.05 0.2068 0.518

Center 84.67 2.670 0.806

86.51 0.1543 0.261 82.46 2.187 3.814

Bottom

86.89 < 0.051 < 0.030 84.85 0.426 2.929 86.9 0.0219 < 0.030

Bottom

87.76 < 0.051 < 0.030 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

Balance - Silver (5%) and Copper (7%)


Trials With Iridium & Ruthenium

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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

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


Observation

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• 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.


Trials With Iridium & Osmium in 500 gm Shapet Furnace

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Sample weight - 300 gms (Ref 4) Sample weight - 300 gms (Ref 17)

Element/Position Au (89.3%) Ag (5%) Cu (5%) Ir (0.3%) Os (0.4%) Element Au (89.3%) Ag (5%) Cu (5%) Ir (0.3%) Os (0.4%)

Top

89.5 5.296 5.195 < 0.010 < 0.010

Top

89.11 5.305 5.57 < 0.010 < 0.010 89.47 5.366 5.152 < 0.010 < 0.010 88.74 5.463 5.646 0.025 0.0613 89.23 5.459 5.213 < 0.010 < 0.010 89.57 5.381 5.045 < 0.010 < 0.010 89.48 5.279 5.226 < 0.010 < 0.010 88.83 5.336 5.667 < 0.010 < 0.010 89.49 5.346 5.161 < 0.010 < 0.010 88.65 5.406 5.764 < 0.012 < 0.050 89.37 5.419 5.199 < 0.010 < 0.010 88.99 5.304 5.604 < 0.010 0.0503

Centre 89.11 5.391 5.085 0.2085 0.202

Centre 87.01 5.351 5.148 0.4091 2.048

89.45 5.393 5.115 0.0247 < 0.049 88.45 5.441 5.19 0.446 0.467 87.87 5.368 5.063 0.76 0.934 89.13 5.472 5.175 0.0887 0.125

Bottom

89.47 5.42 5.097 < 0.010 < 0.010

Bottom

89.38 5.429 5.178 < 0.010 < 0.010 88.69 5.358 5.15 0.1972 0.597 89.27 5.461 5.257 < 0.010 < 0.010 88.58 5.349 5.016 0.0709 0.977 89.07 5.475 5.441 < 0.010 < 0.010 88.43 5.318 5.141 0.478 0.618 89.24 5.417 5.314 < 0.010 < 0.048 89.53 5.381 5.077 < 0.010 < 0.010 89.47 5.346 5.182 < 0.010 < 0.010 89.49 5.456 5.046 < 0.010 < 0.010 89.55 5.321 5.12 < 0.010 < 0.048


Trials With Iridium & Osmium in 2 kg Induction furnace

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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%) Element/Position Au (89.3%) Ag (5%) Cu (5%) Ir (0.3%) Os (0.4%)

Top

89.23 5.448 5.229 < 0.010 < 0.010

Top

89.22 5.329 5.376 < 0.010 < 0.010 89.35 5.466 5.176 < 0.010 < 0.010 89.19 5.552 5.244 < 0.010 < 0.010 89.19 5.364 5.35 < 0.010 < 0.049 89.2 5.464 5.262 < 0.010 < 0.010 89.07 5.406 5.16 < 0.010 < 0.010 88.91 5.569 4.747 < 0.010 < 0.010 89.16 5.421 5.363 < 0.010 < 0.010 88.78 5.467 5.399 < 0.010 < 0.010 89.21 5.399 5.265 < 0.010 < 0.010 88.79 5.459 5.636 < 0.010 < 0.010

Centre 89.09 5.416 5.076 0.2081 0.205

Centre 88.99 5.422 5.203 0.133 0.246

89.19 5.308 5.066 0.1931 0.243 88.72 5.429 5.18 0.45 0.21 89.12 5.374 5.074 0.386 < 0.048 88.51 5.386 5.224 0.0894 0.776

Bottom

89.65 5.447 4.892 < 0.010 < 0.010

Bottom

89.27 5.446 5.253 < 0.010 < 0.010 89.47 5.494 5.018 < 0.010 < 0.047 89.41 5.438 5.144 < 0.010 < 0.010 89.55 5.447 4.992 < 0.010 < 0.010 89.22 5.564 5.206 < 0.010 < 0.010 89.46 5.471 5.015 < 0.010 < 0.047 89.39 5.332 5.273 < 0.010 < 0.048 89.54 5.287 5.165 < 0.010 < 0.047 89.33 5.525 5.14 < 0.010 < 0.010 89.6 5.402 4.988 < 0.010 < 0.010 89.4 5.454 5.139 < 0.010 < 0.010


Trials With Iridium & Osmium

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Gold with Iridium (0.3%) and Osmium (0.4%) in 500 g furnace for 100, 200 and 300 g lot. Using Furnace 1

Gold with Iridium (0.3%) and Osmium (0.4%) in 2 kg furnace for 100, 200 and 300 g lot. Using Furnace 3


Observation

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• 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 un-predictable.

• Osmium tends to form Osmium tetraoxide above 400 C and is highly volatile.

Inference : Predominantly detection at centre and bottom.

Scanning Electron Microscope 5.

35


XRF Analysis

36

PGM ANALYSIS SAMPLES FOR IIT (DELHI)

Sample No. Au Ag Cu Ir Os Ru

Sample wt. % % % % % %

1 89.50 3.00 7.00 0.50 19.35

2 87.50 4.00 8.00 0.50 19.51

3 88.00 5.50 6.00 0.50 19.56

4 87.00 4.00 7.00 1.00 0.50 0.50 19.53

An MKS PAMP GROUP Company 37

Samples for SEM

Top Surface Bottom Surface Cross Section

Top

Cross section

Bottom

0 - Centre 1 - Near centre 2 - Between centre and circumference 3 - Close to circumference


Gold – Iridium System

38

Top

Cross section

Bottom

Distribution of Iridium Circumference Centre

Top Locations Loc 0 Loc 1 Loc 2 Loc 3

% Composition 1.94 2.36 3.84 4.66

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

Iridium moves towards the periphery of the mold during pouring, but being much heavier tends to migrate towards the bottom


SEM Imaging of Gold Iridium System

39

Top Surface

Cross section

Bottom Surface

Centre Circumference intermediate


SEM Imaging of Gold Iridium System

40

Bottom Surface Centre

Distributed uniformly but seems to form elongated clusters.


Gold – Ruthenium System

41

Top

Centre

Bottom

Distribution of Ruthenium

Circumference Centre

Top Location Loc 0 Loc 1 Loc 2 Loc 3

% Composition 15.1 1.94 0.25 1.13

Cross section Location Loc 0 Loc 1 Loc 2

% Composition 1.03 0.05 0.945

Bottom Location Loc 0 Loc 1 Loc 2

% Composition 0 0.7 1.215

Ruthenium being lighter tends to float and predominantly moves to the top


SEM Imaging of Gold Ruthenium System

42

Top Surface

Cross section

Bottom Surface



SEM Imaging of Gold Ruthenium System

43

Top Surface Centre

Dispersed in irregular manner, showing big lumps or clusters .


Gold – Osmium System

44

Top

Centre

Bottom

Distribution of Osmium

Circumference Centre

Top Location Loc 0 Loc 1 Loc 2 Loc 3

% Composition 4.02 3.85 3.05 3.27

Cross section Location Loc 0 Loc 1 Loc 2

% Composition 3.48 3.17 2.915

Bottom 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.


SEM Imaging of Gold Osmium System

45

Top Surface

Cross section

Bottom Surface



SEM Imaging of Gold Osmium System

46

Bottom Surface intermediate

Cluster formation is least; more dense, round spots.


Gold – Iridium-Osmium-Ruthenium System

47

Top

Centre

Bottom

Distribution in multi-component system

Top Locations Loc 0 Loc 1 Loc 2 Loc 3

% Composition Os 3.78 3.58 3.83 3.78 % Composition

Ir 1.5 2.23 2.58 3.32 % Composition

Ru 0.41 0.62 0.72 0.73

Cross section Locations Loc 0 Loc 1 Loc 2

% Composition Os 3.04 3.69 4.115 % Composition

Ir 2.41 2.41 2.14 % Composition

Ru 0 0.55 0.8

Bottom Locations Loc 0 Loc 1 Loc 2

% Composition Os 2.28 2.22 2.71 % Composition

Ir 0.94 2.08 2.085 % Composition

Ru 2.67 0.63 0.005

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

Osmium Iridium Ruthenium


SEM Imaging of Iridium in the multi-component system

48

Top Surface

Cross section

Bottom Surface



SEM Imaging of Ruthenium in the multi-component system

49

Top Surface

Cross section

Bottom Surface



SEM Imaging of Osmium in the multi-component system

50

Top Surface

Cross section

Bottom Surface


Inferences 6.

51


XRF spectrometer is the need of the hour

52

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.


Trend analysis and data interpretation of samples tested

53

Only Iridium

• 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.

Iridium-Osmium • 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

Iridium-Ruthenium

• 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.

CEN

TER

TOP

BOTT

OM

Bottom

Analysis Points

Center

High value detection predominantly towards Bottom and center.

CEN

TER

BOTT

OM

TOP

Top

Analysis Points

Center

High value detection predominantly towards Top and center.

High value detection predominantly towards Center and bottom.

CEN

TER

TOP

BOTT

OM

Bottom

Analysis Points

Center


Research team

54

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

27

THANK YOU

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