3. Cyanide is used in heap
leach pads to complex
gold and silver in the
mining industry
Cyanide detoxification is
required for mine closure.
PSI’s bio-detoxification
process, which uses native
bacteria, has proven to be
more efficient than
conventional chemical
processes
Bacteria culture used in cyanide detox
4. Pintail Systems, Inc. was founded in 1987 by
Leslie Thompson
Primary focus was on cyanide detoxification in
gold and silver heap leach pads using native
bacteria cultures.
5. In 1991,The Hecla
Mining Company
contracted with PSI to
develop a treatment
process for the Yellow
Pine Mine using
native bacteria
cultures.
6. Located Near Yellow
Pine, Idaho
Alpine Climate
1.2 Million Ton Spent
Ore Heap
Environmentally
sensitive area
7. Detox Goals
To degrade WAD cyanide
to 0.2 mg/L or less in heap
leachate solutions in one
operating season
Prior to contracting with
PSI, Hecla investigated
chemical methods and was
quoted 2 to 4 operating
seasons.
Heap Bio-Detox
WAD Cyanide in Heap Effluent Solutions
0
10
20
30
40
50
1
29
25
50
59
71
85
94
107
114
121
128
136
146
155
Time, Days
WADCyanide
8. Detox goal of 0.2 mg/l
WAD cyanide was achieved
in one operating season,
(155) days
During the detox process,
there was a significant
increase in gold production
Increased gold production
was unexpected and more
than paid for the detox
process
9. Increased gold recovery paid for mine
operations through the end of detox
Mine closure was signed off by the Idaho
Department of Environmental Quality
The Hecla Mining Company won the 1992
Pacific Northwest Pollution Control
Association’s Idaho Award for the
Innovative use of Bacteria in Improving
Water Quality
11. Detox goal was 0.2
mg/L total cyanide in
heap leachate solution
12. Total cyanide closure
goal of <0.2 mg/L TCN
met in 111 days
Significant Gold
Recovery Improvement.
>3000 oz.
Mine closure signed off
by the State of Arizona
DEQ
13. Located near Victor,
Colorado
5 million ton cyanide-
leached spent ore heap
Heap was water-rinsed
for 4 years prior to bio-
detox
Average detox solution
temperature = 35 deg F
Altitude 10,000 ft above
sea level.
14. Detox Goals
Detox WAD cyanide
to 0.2 mg/L in heap
leachate solution
Decrease the bond
requirement for
closure by the state of
Colorado
15. l
Cripple Creek WAD Cyanide
0
0.5
1
1.5
2
2.5
3
1 24 47 70 93 116 139 162 185 208 231 254 277 300 323 346
time, days
leachateWADCN,mg/L
Cripple Creek Gold Recovery
0.00
1000.00
2000.00
3000.00
4000.00
5000.00
6000.00
1 26 51 76 101 126 151 176 201 226 251 276 301 326 351
time, days
cumulativeouncesgold
Increased gold recovery during
cyanide detox
Met the goal of 0.2 mg/L WAD
cyanide in heap leachate solution
in 346 days
16. CC&V water rinse and peroxide treatment (30 pore
volumes) did not detoxify cyanide to regulatory limits
Pintail bio-detox achieved cyanide limits with
application of less than 3 pore volumes of treatment
solution
Bond requirement for mine closure was reduced
Increased gold recovery paid for the detox process.
The detox process actually became a profit center for
the mine.
17. Yellow Pine
1.2 million tons
Cyprus
Copperstone
1.3 million tons
Cripple Creek
Victor
5 million tons
Cyanide
Concentration at
start of detox
50 mg/L WAD CN
in heap leachate
solution
20 mg/L TCN in heap
leachate solution
Just over 3 mg/L
WAD CN in heap
leachate solution
Cyanide
concentration at
end of detox
< 0.2 mg/L WAD
CN heap leachate
solution
< 0.2 mg/L TCN in
heap leachate solution
< 0.2 mg/L WAD CN
in heap leachate
solution
Gold Recovery > 2700 >3000 oz >6700 oz
Treatment Days 155 days 111 days 350 days
Regulatory
Goals Met
Yes Yes Yes
18. 1
Technical advances have produced more gold over the
last 160 years than the previous 6000.
2
Majority of gold produced in the U.S. is from the Heap
Leaching Process
3
Heap Leaching leaves 25 – 40% of the original gold in
the ore at mine closure
Pintail Bio-Processes are the solution to economically
recover heap gold4
19. Cyanide typically recovers 55% to 75% of the
gold in a heap leach pad. 25% to 45% residual
gold is left in the heap.
Using PSI’s microbial treatment system has
been shown to get significant recovery of
residual gold during cyanide detoxification.
20. Ore Tonnage Ore Grade
(oz/ton)
Estimated
Total
remaining
gold (oz)
Estimated
PSI gold
recovery
Mine A 71,000,000 0.009 642,550 417,657
Mine B 81,000,000 0.008 648,000 421,200
Mine C 68,000,000 0.007 465,000 302,250
Mine D 23,000,000 0.008 174,000 113,100
Mine E 36,000,000 0.009 324,000 210,000
Mine F 150,000,000 0.010 1,500,000 975,000
Mine G 170,000,000 0.005 850,000 552,500
Totals 650,000,000 4,603,550 2,992,307
21. $1100/ oz gross $1300/ oz gross $1500/ oz gross
Estimated
PSI Gold
Recovery
$900/ oz net $1100/ oz net $1300/ oz net
Mine A 417,657 $375,891,300 $459,422,700 $542,954,100
Mine D 113,100 $101,790,000 $124,410,000 $147,030,000
Mine F 975,000 $877,500,000 $!,072,500,000 $1,267,500,000
Potential profits based on $200/ oz production cost using PSI Bio Processes
