I have often been curious as to potential economic benefit converting the waste rock would have on our economics. According to the feasibility study:
Within the pit shell there is 171.2 million tonnes of inferred resource grading: 0.25% copper, 0.16 g/t gold, 0.018% molybdenum and 1.58 g/t silver which for purposes of the feasibility study must be treated as waste rock; (CuEq 0.39%)
The follow has lots of assumptions and guesses but I read once a long time ago that when one does estimates on estimates, the end result is often surprisingly close. So here goes.
The first part is straightforward, how much revenue is actually contained in that rock?
copper
|
0.25%
|
958,720 lbs
|
$3.25/lb
|
$3,115,840
|
gold
|
0.16
|
856,000 oz
|
$1445/oz
|
$1,236,920,000
|
molybdenum
|
0.02%
|
69,027 lbs
|
14.64/lb
|
$1,010,568
|
silver
|
1.58
|
8,453,000 oz
|
27.74/oz
|
$234,486,220
|
|
|
|
|
$1,475,532,628
|
|
|
|
|
|
Now assume that the metal recovering is only 86%
|
$1,268,958,060
|
|
|
It will take additional costs (processing) to extract the metals from the rock. I totally guessed at 10%
|
$126,895,806
|
|
|
This gives an expected net revenue of
|
$1,142,062,254
|
Now for another wild guess. let's assume that they run into the waste material in year 7 and it takes 10 years to extract it all. So I took 1/10 of the $1,142,062,254 and applied to each year's NPV discount factor. This gave a chart like:
|
NPV (8%)
|
|
Year
|
1.00
|
|
1
|
0.92
|
|
2
|
0.85
|
|
3
|
0.78
|
|
4
|
0.72
|
|
5
|
0.66
|
|
6
|
0.61
|
|
7
|
0.56
|
$63,709,555
|
8
|
0.51
|
$58,612,790
|
9
|
0.47
|
$53,923,767
|
10
|
0.43
|
$49,609,866
|
11
|
0.40
|
$45,641,076
|
12
|
0.37
|
$41,989,790
|
13
|
0.34
|
$38,630,607
|
14
|
0.31
|
$35,540,159
|
15
|
0.29
|
$32,696,946
|
16
|
0.26
|
$30,081,190
|
17
|
0.24
|
|
18
|
0.22
|
|
19
|
0.21
|
|
20
|
0.19
|
|
|
|
|
|
NPV @ 8%
|
$450,435,746
|
|
|
|
From BFS
|
Base Case NPV
|
$513,000,000
|
|
|
|
|
New Potential NPV
|
$963,435,746
|
So under this wild guess assumptions, the NPV at 8% would go from $513 Million to $963 million. That is a nice improvement.
As a note, if the NPV at 5% is used, the NPV of the waste rock is $640 million. This brings the Base case NPV (at 5%) from $1,694 million to $2,334 million.
Just food for thought.