The document summarizes an assay lab chemistry internship. It describes various projects the intern worked on including analyzing how shaking time affects gold concentration in ore samples and how the volume of preg-rob solution dispensed affects results. It also discusses calibrating an XRF machine to properly measure gold and silver concentrations. The intern found shaking time and contact time with cyanide increased gold concentration as expected. Too little or too much preg-rob solution led measurements outside the average. Applying correction factors and changing error weight types helped improve the XRF calibration.

1. Assay Lab Chemistry Internship
Maggi Braasch-Turi
Summer 2014

2. 2
Overview
 Background
 Projects
– Poor AA:FA Ratio Sample Analysis
– Effect of sitting time on ore samples
– Average Preg Rob Percent on Blast Hole Standard
– Effect of Preg Rob volume with Blast hole standard
– XRF New Gold Pin Method Calibration
 Other tasks
 Challenges
 Future Plans
 Acknowledgements

3. 3
Background
 Home: Owatonna, MN
 College: Rapid City, SD
– South Dakota School of Mines
& Technology
– B.S. Chemistry in 2016
– Activities:
– Alpha Chi Sigma
– American Chemical Society
– Chemistry tutor
 Other Experiences
– ACS Undergraduate Award for
Analytical Chemistry
– Sanford Underground Research
Facility MAJORANA Temporary
Clean Room

4. 4
Poor AA:FA Ratio Sample Analysis
 Purpose: To analyze the effect shaking time has on ore samples with
poor AA:FA ratios
 Hypothesis: AA:FA ratios will increase with longer shaking time
 Procedure:
1. Put 10.00g of each sample into the 50mL centrifuge tubes
2. Put one pump of CN- in each tube
3. Shake for the allotted time
4. Centrifuge for 10 minutes
5. Decant immediately into the Varian test tubes
6. Analyze with the AA

5. 5
Poor AA:FA Ratio Samples
 Conclusion: As predicted, the AA:FA ratios increased significantly with longer
shaking time.
0.64
0.56
0.66
0.58
0.42
0.74
0.89
0.94 0.95 0.98
0.89
0.99
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
8:35 9:00 9:50 11:20 12:50 14:35
Au(oz/ton)
CH-051314-02 Samples
Shaking Time vs. Concentration
Original 1 Hour 1 Hour ReRun 2 Hours 3 Hours Original Ratio 3 Hour Ratio

6. 6
Average AA:FA Ratio Samples
 Purpose: To analyze the effect shaking time had
on a mixture of ore samples with good and bad
AA:FA ratios
 Hypothesis: AA:FA ratios will increase with
longer shaking time
 Samples with average original AA:FA ratios served
as a control
 Same Procedure

7. 7
Average AA:FA Ratio Samples
 Conclusion: AA:FA ratios only increased with longer shaking time in the case of
samples with poor ratios. Samples with average ratios did not increase significantly.
 This test confirms that shaking time alone was not the only issue with the poor samples.
0.90 0.93
1.00 0.98
0.92
0.68
0.76
0.89
0.50
0.85
0.59
0.91 0.95
0.90 0.94 0.96 0.95 0.91
0.81 0.80
0.94
0.57
0.86
0.81
0.97 0.94
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
Au(oz/ton)
Samples
Concentration vs Shake Time
Experiment #2
Original 1 Hour 2 Hours 3 Hours Original Ratio 3 Hour Ratio
Values BELOW the dots are the Original Ratio
Values ABOVE the dots are the 3 Hour Ratio

8. 8
Side by Side Comparison
0.64
0.56
0.66
0.58
0.42
0.74
0.90 0.93
1.00 0.98
0.92
0.68
0.76
0.89
0.50
0.85
0.59
0.91
0.95
0.89
0.94 0.95 0.98
0.89
0.99
0.90
0.94 0.96 0.95
0.91
0.81 0.80
0.94
0.57
0.86
0.81
0.97 0.94
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
Auoz/ton)
Samples
Shaking Time vs Concentration of Au
Complete List
ORIGINAL 1 HOUR 1 HOUR RERUN 2 HOURS 3 HOURS ORIGINAL RATIO 3 HOUR RATIO
Values BELOW the dots are the Original Ratio
Values ABOVE the dots are the 3 Hour Ratio

9. 9
Particle Size of Gold
 Scanning Electron Microscope at Goldstrike
 They told us that particle size was not an
issue because they only found one piece
larger than 2.5 microns

10. 10
Effect of sitting time on ore samples
 Purpose: To analyze the effect of sit time has on the
AA:FA ratio on samples with poor AA:FA ratios
 Hypothesis: The sit time will increase the AA:FA ratio
because the CN- is in contact with the gold, affecting the
results and purpose of the test
 Procedure:
1. Put 10g of each sample into the 50mL centrifuge tubes
2. Put one pump of CN- in each tube and shake for one hour
3. Sit out for the determined time (overnight, over the weekend)
4. Centrifuge for 10 minutes
5. Decant immediately into the Varian test tubes
6. Analyze with the AA

11. 11
Sit Time
 Conclusion: The ratios did increase, as expected, because the gold was in
contact with CN-. This confirms that the longer the gold is in contact with CN- ,
the ratio will increase enough to skew the results for poor samples.
0.64
0.56
0.66
0.58
0.42
0.74
0.90
0.97 0.98
1.03
0.98
1.04
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
8:35 9:00 9:50 11:20 12:50 14:35
Au(oz/ton)
Sample
Concentration vs Sitting Time
Original Immediately Overnight Weekend Original Ratio Weekend Ratio

12. 12
Preg Rob Analysis with BH Standard
 Purpose:
– To get a average Preg Rob percent using the blast hole standard
– To see how inaccurate dispensing of Preg Rob solution (or any solution)
can affect results
 Hypothesis: Concerning dispensing the solutions:
– Adding too much will cause there to be too much gold in solution, thus
causing some to be absorbed by the carbon in the standard via equilibrium
 Procedure:
1. Put 10g of BH standard into the 50mL centrifuge tubes
2. Put one pump (at specific volumes) of Preg Rob in each tube and shake for one hour
3. Centrifuge for 10 minutes
4. Decant immediately into the Varian test tubes
5. Analyze with the AA
Au(s) + 2CN-
(aq, excess)⇌ [Au(CN)2]-
(aq)

13. 13
Preg Rob Results
 Conclusion: Most of the standards are within the first standard
deviation, except for a few spots, which were on purpose.
0.1990
0.1700
0.1800
0.1900
0.2000
0.2100
0.2200
0.2300
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101105109113117121125129133137141145149153157
Au(oz/ton)
Sample #
Standard Preg RobPR AA oz/ton Average std 1 up down std 2 up down std 3 up down

14. 14
Preg Rob Percentages
 All negative PR% are reported as zeros
 The average was 2.44%, excluding the last 40 sample points.
2.44
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101105109113117121125129133137141145149153157
Percentage
Sample
PR %
Preg Rob % Average PR% value

15. 15
Patches of zeros
 Most all of the reported zeros were negative PR values.
 I looked into see why.
 Amount of solution had something to do with it, so I did
both.
– 20 samples each
– 121-140 with 21g of CN- solution
– 141-160 with 18g of CN- solution

16. 16
Volume and Preg Rob %
• Conclusion:
• Adding too little brings the concentrations far outside the mean because nothing is being absorbed. All of the gold is
being analyzed and not absorbed.
• Adding too much lets more gold be absorbed.
2.44
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
1
8
15
22
29
36
43
50
57
64
71
78
85
92
99
106
113
120
127
134
141
148
155
Percentage
Sample
PR %
Preg Rob % Average PR% value
21g
18g
0.1990
0.1700
0.1800
0.1900
0.2000
0.2100
0.2200
0.2300
1
8
15
22
29
36
43
50
57
64
71
78
85
92
99
106
113
120
127
134
141
148
155
Au(oz/ton)
Sample #
Standard Preg Rob
PR AA oz/ton Average std 1 up
Type equation here.

17. 17
XRF Calibration
 Purpose: To get the new gold standard discs to calibrate
and measure properly
 Issues:
– Au curve didn’t go through zero
– Causing the concentrations to be read incorrectly
y = 0.5349x + 44.138
R² = 0.9574
0.0000
20.0000
40.0000
60.0000
80.0000
100.0000
0 20 40 60 80 100
CalculatedAu%
Standard Au%
Before Gold Blank CCalc Au %
y = 0.9972x + 0.2221
R² = 0.9972
-10.0000
10.0000
30.0000
50.0000
70.0000
90.0000
0 20 40 60 80 100
CalculatedAu%
Standard Au %
After Gold Blank CCalc Au %

18. 18
What I tried
 Sample details
– Taking into account mass and diameter,
accurate and average
– Changing measuring time
– Green denotes data within ±1% of FA
values.
– 2 samples were within the range for
Au and most were in range for Ag
– Not good

19. 19
After calling PANalytical
 Gold blank as a standard
 Modifying the application to include:
– Correction Factors
–FP
– Error Weight Type
–Absolute
–Square Root

20. 20
Gold Blank
 Robert made a silver proof for
me- about 29.936g and 32mm
 Adding it brought the line
through zero
– Put a point near zero pulling the
line down with real data
 Green denotes data within ±1%
of FA values.
– More green, but not as good as
it needs to be

21. 21
Correction Factor
Used FP (Fundamental Parameters)
– Math that takes into account what we told it to be
verses what is measures
– Adjusts the data points to fall into the curve better
– Good for long ranges of points
 Reds are out of range
 Greens and browns are
within the ±1%.
Standards run as samples
before correction
Standard XRF READ Au % XRF READ Ag% % DIFF Au % Diff Ag
99.999 97.1220 1.7410 2.8770 -1.7410
98/2 96.9750 2.7910 1.0250 -0.7910
96/4 95.4970 4.2420 0.5030 -0.2420
92/8 93.8590 7.0240 -1.8590 0.9760
88/12 90.7310 10.0320 -2.7310 1.9680
0/99.999 -0.2310 99.9840 0.2310 0.0150
after FP correction (Au, Ag)
(Absolute, Absolute) Error Weight Type DEFAULT SETTING
Standard XRF READ Au % XRF READ Ag% % DIFF Au % Diff Ag
99.999 98.8470 -0.6140 1.1520 0.6140
98/2 97.9090 1.2440 0.0910 0.7560
96/4 96.4130 3.7860 -0.4130 0.2140
92/8 93.6010 8.4980 -1.6010 -0.4980
88/12 87.7780 13.3280 0.2220 -1.3280
0/99.999 -0.0730 99.5210 0.0730 0.4780

22. 22
Error Weight Type
 Absolute
– Good for wide range data
– Looks at the entire spectrum
 Square Root
– Takes the square root of
the error value
– Makes the error smaller
– Works best for points that
are very close together
after FP correction (Au, Ag)
(Absolute, Absolute) Error Weight Type
CCalc Au % Ccalc Ag% % DIFF Au % Diff Ag XRF READ Au % XRF READ Ag% % DIFF Au % Diff Ag
99.0068 -0.0153 0.9922 0.6231 98.8470 -0.6140 1.1520 0.6140
97.9981 1.7838 0.0019 0.7664 97.9090 1.2440 0.0910 0.7560
95.9807 4.2354 0.0193 0.2364 96.4130 3.7860 -0.4130 0.2140
92.9336 8.7994 -0.9336 -0.4737 93.6010 8.4980 -1.6010 -0.4980
88.1532 13.5340 -0.1532 -1.3599 87.7780 13.3280 0.2220 -1.3280
-0.0734 97.2761 0.0734 0.2078 -0.0730 99.5210 0.0730 0.4780
(Absolute, Square Root) Error Weight Type
CCalc Au % Ccalc Ag% % DIFF Au % Diff Ag XRF READ Au % XRF READ Ag% % DIFF Au % Diff Ag
99.0068 -0.6231 0.9922 0.0153 98.5360 -0.0080 1.4630 0.0080
97.9981 1.2336 0.0019 0.2162 97.7010 1.7880 0.2990 0.2120
95.9807 3.7636 0.0193 -0.2354 96.2420 4.2480 -0.2420 -0.2480
92.9336 8.4737 -0.9336 -0.7994 93.4930 8.8100 -1.4930 -0.8100
88.1532 13.3599 -0.1532 -1.5340 87.7250 13.4930 0.2750 -1.4930
-0.0734 99.7912 0.0734 2.7229 -0.0730 97.0110 0.0730 2.9880
• Does more math to correct points based upon each scenario
• Both are pretty close. So
I asked for PANalytical’s
recommendation.
• They recommended
Absolute for Au and
Square Root for Ag

23. 23
XRF Samples
 Used pin samples from last months
inventory
 Filled in the blanks of data
 Green-needed Gold Pin Method (old
method)
 Blue- needed Fire Assay
 White- had all data
 Navy- pins did not roll out well
enough for XRF analysis
Average Diameter
(mm)Samples Mass (g)
P19496-04 9.638 28.125
P19505-13 10.804 31.5
P19514-23 9.928 30
P19524-26 8.539 30.625
P19527-36 12.398 35.625
P19537-46 7.973 29.25
P19547-49 10.652 33.75
P19550-59 12.041 33.125
P19560-68 8.045 35.75
P19569-72 12.748 41.25
P19573-75
P19576-83
P19584-90
P19591-98 7.875 26.25
P19599-606 11.321 30
P19607-12
P19613-21 11.558 32.25
P19622-27 13.025 34
P19628-35 10.495 34
P19636-42 11.803 30.25
P19643-50 12.05 30.25

24. 24
XRF Samples
– Accurate mass and average
diameter
– Mass and diameter set to 1g/1mm
– 500g/60mm
– No mass or diameter input
 I made observations on
each pin sample as well
 The following will negatively
affect XRF analysis:
– Sample too small
– Cracks
– Not flat
– Face is not uniform
Observations of the sample
Samples
P19496-04 almost not wide enough
P19505-13
P19514-23 large crack
P19524-26 not quite wide enough for window without cracks, 2
P19527-36 not quite flat,
P19537-46 cracks and etchings on one side
P19547-49 not flat
P19550-59
P19560-68 long crack in window, not flat,
P19569-72 not flat, dark impurity marks- from roller?
P19573-75
P19576-83
P19584-90
P19591-98 not big enough for the window without cracks in it
P19599-606 not wide enough for window
P19607-12
P19613-21 not flat
P19622-27 not big enough for the window, 2 cracks
P19628-35 large enough to cover window, but hairline cracks are in window too, 3
P19636-42 almost too short to cover window, not completely flat
P19643-50 almost too short to cover window, 2 hairline cracks that could impede analysis
The samples were analyzed with the following parameters
using the New Gold Pin Method:

25. 25
Samples with Imperfections
Average
Diameter (mm)
FA GPM % Diff NGPM % Diff
Flags Samples Mass (g) Au% Ag% Au% Ag% Au% Ag% Au% Ag% Au% Ag%
P19496-04 9.638 28.125 88.892 1.817 88.772 2.198 0.12 -0.381 88.772 1.597 0.12 0.22
P19505-13 10.804 31.5 89.249 2.233 89.437 2.443 -0.188 -0.21 89.501 2.011 -0.252 0.222
P19514-23 9.928 30 89.199 2.224 88.659 2.421 0.54 -0.197 88.657 1.969 0.542 0.255
P19524-26 8.539 30.625 85.484 2.573 85.835 2.623 -0.351 -0.05 85.882 2.323 -0.398 0.25
P19527-36 12.398 35.625 88.712 1.48 88.465 2.022 0.247 -0.542 88.008 1.294 0.704 0.186
P19537-46 7.973 29.25 89.275 1.757 89.388 2.074 -0.113 -0.317 89.122 1.377 0.153 0.38
x P19547-49 10.652 33.75 87.853 2.153 83.411 2.314 4.442 -0.161 90.502 1.769 -2.649 0.384
P19550-59 12.041 33.125 88.511 4.053 85.181 3.682 3.33 0.371 88.911 4.097 -0.4 -0.044
x P19560-68 8.045 35.75 86.917 5.244 84.665 4.59 2.252 0.654 90.009 5.576 -3.092 -0.332
P19569-72 12.748 41.25 87.283 5.354 84.634 4.636 2.649 0.718 86.806 5.655 0.477 -0.301
P19573-75
P19576-83
P19584-90
x P19591-98 7.875 26.25 84.302 5.059 86.47 5.209 -2.168 -0.15 84.701 6.542 -0.399 -1.483
x
P19599-
606
11.321 30 84.771 5.059 87.034 4.459 -2.263 0.6 89.366 5.311 -4.595 -0.252
P19607-12
P19613-21 11.558 32.25 86.937 4.013 88.796 3.653 -1.859 0.36 87.028 4.309 -0.091 -0.296
P19622-27 13.025 34 87.993 3.392 88.678 3.306 -0.685 0.086 88.82 3.448 -0.827 -0.056
P19628-35 10.495 34 87.722 3.383 88.381 3.324 -0.659 0.059 87.809 3.452 -0.087 -0.069
P19636-42 11.803 30.25 88.63 2.039 84.452 2.28 4.178 -0.241 88.277 1.683 0.353 0.356
x P19643-50 12.05 30.25 87.825 1.866 82.668 2.17 5.157 -0.304 92.142 1.529 -4.317 0.337
x P19651-59 10.701 29.25 86.399 1.441 85.497 1.809 0.902 -0.368 90.144 0.909 -3.745 0.532
P19660-68 11.692 30.375 86.567 1.407 85.572 1.792 0.995 -0.385 86.454 0.89 0.113 0.517
Samples with imperfections did not analyze within ±1% the FA value.

26. 26
Sample details effects conclusion
 Mass is not a huge factor unless way out of range
– 1g/1mm was pretty true to FA
– 500g/60mm was incredible out of range
 Most accurate results with sample inputs of:
– Accurate mass
– Average (approximate) diameter

27. 27
How to fix the sample prep?
 Uniform sample diameter
– Use the molds that Jerry bought
–~33mm
– Eliminates varying diameters
 Able to have a set diameter in program
– Would only need to input mass

28. 28
Other Things I’ve Learned
 Pulp Weigh
 XRF Carbon sample prep
 Running AA’s
 Helping in the Wet Lab
 Made solutions
– 6#/ton Cyanide
– Preg Rob
 6#/ton Cyanide Titration with silver nitrate

29. 29
Challenges
 EXCEL
 The slowness of the XRF computer
 Troubleshooting calibration issues on existing methods

30. 30
My Future Plans
 Graduate School for a Master’s Degree
– Organic- so far
– Possibly pharmaceuticals
– Still have Physical and Inorganic Chem
Basic benzaldehyde ^ ^Same solution with Thiamine HCl added to it.
Start of the synthesis to make Phenytoin and anti-epileptic drug.
Benzipinacol crystals from the
Photochemical reaction of
benzophenone with IPA and light

31. 31
Thank you!
 Barrick Gold- Process Division
 Jerry Vandergriff
 Gayle Fitzwater?
 Nancy Plummer
 Eric Brown
 Dawn Gann
 All of the Crews
Beep beep motherfuckers!

32. 32
Questions?