August 2016 Doug Beattie, Mining Engineer (Retired)
This is an article written some time ago by Doug Beattie. It is part of a series called Zinc Mining Ramblings, which were published on an internet location managed by Doug which is no longer accessible at the moment, but can be found in its entirety here (see the links in the comment section below the linked article). He was so generous to let Criticalinvestor.eu republish any article we wanted to, under the condition that we would make several things clear for readers before they continue with the article:
- Readers should be made well aware that Doug Beattie is retired and has not accepted, and will not accept, any compensation for the reports he has written. Once compensation comes into the equation, it takes away some of his editorial liberty and would likely cause him to become very cautious with what he has to say.
- Secondly, he has based his assessment on publicly available information only, hence he does not have the "inside angle" that analysts at the brokerages, traders etc. have. Since most of these modules were written over two years ago, many of the links are no longer functional.
- That Doug cannot be held liable for anything he has written in his articles
- That these reports are often on the whimsical side and readers should bear this in mind.
- That Doug has given us permission to republish.
- Criticalinvestor.eu cannot be held liable for anything Doug Beatty has written in his articles, and does not necessarily agree with parts or all of its contents. Notwithstanding this, Criticalinvestor.eu believes parts or all of its contents, being the opinions of Doug Beatty as a retired mining engineer, could be useful for informational purposes and a potential starting point for your own due diligence.
- Pictures, charts, videos etc were left out when a source was not available or written permission available
- All presented tables are Doug’s own material, unless stated otherwise.
Biography of Doug Beattie
Doug Beattie is a retired Chief Mine Engineer of Cameco, one of the largest uranium producers in the world, and is knowledgeable on uranium mines and mining. He also spent approximately eight of his 30+ years in the mining business working as an engineer at zinc mines including Noranda’s Geco copper/zinc/silver mine in northern Ontario, and Glencore’s George Fisher and McArthur River zinc/lead/silver mines in northern Australia. Doug Beattie graduated in mining engineering at Queen’s University.
After working as a mining engineer in Saskatchewan, Ontario and Australia, he joined Cameco Corporation in 1993 as Senior Mining Engineer at the McArthur River exploration project. He later became Engineering Superintendent during the construction phase, and Mine Superintendent during the ramp-up to full production. In 2002 he became the Corporate Chief Mine Engineer at Cameco’s head office where he was largely involved in uranium project assessments and studies. He then consulted on a number of projects in Canada and Europe before full retirement in 2015.
This sums up the biography of Doug, his article is next, enjoy:
The purpose of this module is to get an understanding of the zinc mining production potential in Australia. By looking at numerous significant zinc mining countries it is then possible to form educated opinions on the relative health of the industry to determine whether the market is heading for oversupply or deficit assuming steady or increasing demand. Summary findings are illustrated below in Table 1. Zinc mine production levels have fallen by over 40% and will only partially recover from there.
Projects on the drawing board and exploration prospects will be covered in Part II but the impact of these projects is likely to only have a minor effect on +2020 production levels.
Zinc mining in Australia is a bit of a good news, bad news story. The good news is, unlike Canada, the zinc mining industry remains somewhat vibrant. The bad news is that a lack of exploration in the past twenty years has meant that what is currently being mined was almost exclusively discovered before 1990. The potential to find more deposits in Australia is still excellent in my mind and the logistics and operating conditions for a mine there are generally very good providing there is good access to water. Mines in Canada spend a huge amount of capital on ensuring they can survive a harsh winter whereas in Australia, the mill, for instance, can be outdoors exposed to the elements. This is a huge competitive advantage.
As a young snot nosed engineer, I moved to Australia in 1988 to take a mining engineering job with Mt. Isa Mines Ltd (later bought by Xstrata, now themselves part of Glencore). My role there was to help get the Hilton silver/lead/zinc mine off the ground production wise and then figure out what we were going to do with Hilton North. The Hilton Mine is now called George Fisher (P49) and Hilton North is now called George Fisher (L72). So essentially I laid out many kilometers of tunnels and designed blasthole stopes up to 400,000 t each and spent some time supervising miners underground. After we hit our stride at Hilton and had the plan in place to access Hilton North from underground, I was transferred to Brisbane to supervise the underground design for the McArthur River zinc mine in the Northern Territory. I left Australia before this plan was implemented but essentially they followed what I laid out for many years. The mine has since converted to an open pit mine once the mill got more confidence treating the other numerous fine grained and high pyrite ore zones and permission to move the river was obtained from the Northern Territory government.
George Fisher and McArthur River are now the two largest zinc mines in Australia and are firmly planted in the top 10 for the world. I also had the opportunity to travel around Australia and the world to see what many of the other zinc miners were up to. So, unlike India, I feel uniquely qualified to discuss zinc mining in Australia.
A common thread in the Australian zinc mining industry, and indeed in other nations, is that many of the operations were at one time considered to be lead/silver mines since this is where the profits were. Zinc was of secondary importance. Where is was possible to mine lead and silver rich orebodies in preference to zinc rich zones, such as at Broken Hill and Mt. Isa, this was done. The Australian zinc mining industry is now dominated by companies that own zinc smelters (or feed state owned smelters such as in China’s case). Zinc is now the primary metal extracted and it must now be the profit center due to generally lower lead and silver grades. This is a very important transition that has occurred. However, what has not changed is the relationship between zinc, lead and silver commodity prices. This has deteriorated. As illustrated in the graphs below the relationship between the three commodities has actually turned away from zincs favour.
Prior to 2005 zinc traded at twice the price of lead and this ratio is now closer to 1:1. One ounce of silver typically traded at 12 times the price of a pound of zinc but this ratio is now closer to 16:1.
The net result of this is that a mine which now must survive on zinc may very well find itself bankrupt as we have seen in numerous cases. It is one of the primary reasons why there has been very little investment in the industry. It is also a key reason why smelters have had to get into the mining business and run mines at considerable losses on occasion. They would not have a guaranteed source of zinc concentrate supply otherwise.
I am sure zinc miners are grateful for the fact that the zinc price has stabilized post-2009 at a level twice that of prior to 2004. But the fact of the matter is, this is grossly insufficient to incentivize an industry to seek out and develop new production centers. Consumers have failed to recognize that zinc is no longer a byproduct at most mines. It is the primary metal mined. This therefore provides an opportunity for those who realize this cannot persist.
It is instructive to note that the silver/lead/zinc deposits at Mt. Isa were always referred to by the original owner, Mt. Isa Mines Ltd, as lead deposits. Glencore now refers to remaining ore as zinc deposits. With a lead smelter on site and silver reporting to the lead concentrate, it was far more profitable in the past to focus on lead rich deposits. These are now largely mined out. Glencore’s motivation for mining the zinc rich remaining deposits appears largely due to the fact that they have a number of hungry zinc smelters to feed around the world. This does not mean it is necessarily more profitable than mining which occurred in the past. Indeed, the cutback announcement made in October 2015 acknowledges this fact.
Next month marks a milestone that will go largely unnoticed, even by those intimately associated with the base metal mining world. Lead/zinc mining, that commenced in 1929, at Mt. Isa will cease.
Underground lead/zinc mining ceased in 2005. The Black Star Open Cut, which mined the up dip extension of the underground deposits, commenced in 2004 but ceases in September due to ore exhaustion. Figure 1 is a cross section through the numerous lead/zinc orebodies. Table 2 lists 2015 production and remaining reserves as of January 1, 2016. Forecast production is discussed later.
One of the key issues with the mining of this pit has been the location of infrastructure on surface. Glencore lists a measured and indicated resource for an expansion of this pit of 236 MT grading 3.7% Zn plus copper, lead and silver but this entails the relocation of the lead/zinc concentrator and other infrastructure to proceed as illustrated in the photo below. The big stack in the photo is the lead smelter. I used to live across the street in behind my favorite watering hole, the Barkly Hotel. If I had something to discuss with the General Manager but could not get his attention during the day, I knew what bar stool he would be sitting on at 5 PM.
As illustrated in Figure 2, George Fisher is really two separate deposits located about 20 km north of Mt. Isa. Both deposits are similar to the Mt. Isa lead/zinc deposits (Figure 1) though much more deformed. A series of orebodies are stacked like pancakes with waste shale between. The Hilton Mine (since renamed George Fisher P49) consists of seven orebodies and the George Fisher L72 area (which we used to call Hilton North) has roughly a dozen zones of ultimate interest though mining is likely confined currently to half of these. The P49 shaft can hoist in excess of 1.5 MT a year and my understanding is the L72 hoisting shaft (not illustrated in Figure 2) can hoist in excess of 3.0 MT a year.
Most orebodies are from 3 m to 25 m wide, dip around 60-65 degrees and can extend laterally for +500 m and down dip for +500 m. There is no lack of ore at George Fisher, it just needs to be mined carefully to avoid excessive dilution. Blasthole stoping and a variant known as bench mining are the standard methods used. I have mentioned blasthole stoping in the Modules often and to get a sense of what it actually is I have included below a picture of a mined out stope from George Fisher. This photo is from a PhD thesis found here. I guess you can say this is largely what I did for a living, making big holes in the ground up to a thousand metres below surface in some very inconvenient places around the world. It was lots of fun actually.
George Fisher was ramped up to a production rate of 4.5 MT per year in 2015 and then quickly knocked back to 3.5 MT per year as part of the cutbacks announced in October 2015 when zinc hit the price of $0.72/ lb.
Table 3 illustrates 2015 production and reserves as of January 1, 2016.
When this asset was owned by Mt. Isa Mines Ltd in the 1980’s and 1990’s our typical annual production grades were 7% Zn, 7% Pb and 120 g/t Ag. So it is readily apparent that this asset has transitioned to being a predominantly zinc asset since then. Below is the P49 production shaft where I used to work.
It is also important to note that previous decisions to expand George Fisher from ~3.8 MT to 4.5 MT a year (and McArthur River from 2.5 MT to 5.5 MT a year and Lady Loretta from 1.0 MT to 1.6 MT a year) were made by Xstrata and not Glencore. Glencore has reversed these decisions and in the case of Lady Loretta, shut it down entirely. Glencore may take plenty of time before they increase production once again.
Near surface mineralization at George Fisher P49 was mined up to 2014 by open pit methods. This pit is now exhausted. Much of this mineralization was oxidized leading to poor mill recoveries. You can see the pit in the above photo just below the water tanks.
This deposit is located 140 km north of Mt. Isa and was discovered over 40 years ago but languished until 2012 when production commenced. It passed through a number of hands prior to Xstrata acquiring it in their Noranda acquisition.
It made little economic sense in the past to develop a full mine/mill site here so Glencore trucks the ore to the mill in Mt. Isa since it now has plenty of spare capacity. Blasthole stoping is used at Lady Loretta and for a sense of what the underground looks like there is a video here .
The mine is rated for 1.6 MT of ore a year. This mine was placed on care and maintenance in October 2015. Table 4 illustrates 2015 production and reserves remaining as of January 1, 2016. At full production therefore, there are only roughly five or six years of mine life remaining with poor prospects of discovering additional resources. This asset will therefore be likely treated as a contractor operated swing producer brought back into production when zinc prices increase markedly.
Mt. Isa Mill
The above assets all feed the mill at Mt. Isa. Listed in Table 5 is the performance of this mill since 2012. Table 6 is a forecast to 2022 assuming the cutbacks are removed as of (say) July 1, 2017. If the cutbacks remain in place indefinitely, total annual production will be less than 200,000 T of zinc in concentrate since only the George Fisher mine will be in operation at reduced production rates.
Table 5 reveals however, that even bringing all production back still does not get production back to 2015 levels due to the loss of production from the Black Star Open Cut.
Messaging from Glencore will be very important. If they announce the removal of cutbacks, the zinc price at that time will likely be deemed by the market to be acceptable to Glencore and could put a ceiling on the zinc price. The proper message is likely to bring some production back but only to partially replace lost production from the Black Star Open Cut and to communicate such.
The McArthur River mine was developed in the early 1990’s not because of its wonderful economics. It was developed because the Northern Territory was putting pressure on Mt. Isa Mines to develop the asset or lose it. In other words, they were threatening us with expropriation although in a very polite typically Australian way. A fact known by only a handful of us. It also nicely coincided with a recession in Australia (Paul Keating’s “The recession we had to have.”) so the federal government was under great pressure to help kick start the economy again. So we fronted up in Canberra to kill two birds with one stone and everyone got great mileage from it. I still have the newspaper clippings.
My task was to put the underground design together. The fundamental problem to this day at McArthur River is the fine grained nature of the mineralization. If you held a piece of high grade drill core in your hand you would be very hard pressed to realize it was metallic ore except for its density. Hermann Radmuller (page 6) and I reopened an old bulk sample decline to get more ore and we shipped it off to Mt. Isa for testing. Those were good times, particularly at Campbell’s Country Club (the camp bar) and the Heartbreak Hotel after work. The metallurgists indicated that they could only make a reasonable bulk concentrate with 2 orebody, 4 orebody and the upper part of 3 orebody. The IsaMill technology was specifically developed during the feasibility study to cost effectively grind the ore to a P80 of 8 microns. Good ole German technology (Netzsch) from the paint industry was scaled up very successfully for the mining industry. (The Caribou mine in Canada can thank us for this adaptation since it is what has made that ore now millable.)
But, due to the metallurgy, my hands were tied to one mining method only, inclined room and pillar mining on two horizons (2 o/b and a 4 o/b 3 HW blend). A great way to sterilize the other orebodies present and not exactly the cheapest method around. This method was used successfully however for over ten years from the mid-90’s during which time 2 orebody was largely mined out producing about 150,000 T of zinc in concentrate annually. During this timeframe, the metallurgists also realized they could mill other ore zones. So the push was made to convert from underground mining to open pit mining. Open pit mining has since been expanded. Final depth will be in the 400 m range. A 34 page description of this expansion can be found here .
The other stumbling block in the past was the presence of the McArthur River itself right over top of the orebody. This was a dry channel for perhaps ten months of the year (and a good place to catch barramundi trapped in the billabongs) but could be a raging torrent over 1 km wide during the monsoonal wet season particularly if a cyclone was in the area. The end of the airstrip would actually be under water. The mill and mine portals to underground were located on Barney Hill safely above the floodplain. The river diversion channel and berm separating river from the open pit is illustrated in the photo below. It was the ability to open pit mine that really blew the doors off the production potential for this mine.
The various orebodies are illustrated in the photo below. The top 50 m of ore (the crown pillar essentially) was very steep before it subsequently flattened out for room and pillar mining.
The key to note is that open pit mining is now sending almost the entire ore package to the mill but much of it is rejected by a heavy media separation plant at the frontend. Table 7 illustrates 2012-2015 production and reserves as of January 1, 2016. However, based upon the zinc in concentrate reported, zinc recovery was only 64.5% in 2015. In other words, the mill has chosen throughput over recovery. Also note the drop in mined ore grade. A 100% increase in throughput since 2012 has only led to a 35% increase in zinc in concentrate. Performance is far short of what was announced in expansion plans.
It is very important to note that the mine produces a bulk concentrate that less than 8% of smelters can treat using the Imperial Smelting process. The process is considerably more expensive than conventional smelters and is therefore reflected in treatment charges. The McArthur River bulk concentrate is unusual in that it has up to 46% zinc which is not far from being a suitable grade for electrolytic smelters. The lead content (roughly 10%) is too high however for electrolytic smelters.
There could be more than meets the eye therefore with respect to the announced cutback in production in October 2015. There may be little or no market for the additional concentrate despite what the price of zinc happens to be. The IZA states that Imperial Smelters are only in operation in China, India, Japan and Poland. Glencore could perhaps blend some of this concentrate with other zinc concentrate to make an acceptable feed for their European smelters. In 2012 Xstrata reported that less than 10% of McArthur River concentrate was used internally however. So my gut feel is that these guys have over run their market and we will not see this mine return to previous production levels since few want what they produce. Table 8 is therefore my estimate of production to 2022. But Ivan could always prove me wrong I guess.
Anyone who knows anything about the zinc industry will be able to tell you that this mine closed last year and this is a prime reason there is a shortage of zinc concentrate. I won’t bother to elaborate on previous mining here at this open pit. Table 9 lists production from 2012 to closure. The mill was used to treat ore from the Dugald River test mining and this is also included in Table 9.
This stalwart has been in operation since 1936 and continues to just keep on giving. A good summary of the operation is found in the Downloads area here . There are some good photos and figures I won’t reproduce here. Looks like a nice place to live and work. The ore zones dip at an awkward 43 degrees but they have still been able to apply variations of blasthole stoping. Mining is being conducted at depths up to 1,500 m. All ore is hauled to surface in 55-60 tonne trucks and this appears to be the site bottleneck. The shaft hoisting of ore to surface ceased in the early 2000’s.
Proven and probable reserves as of June 30, 2015 are:
7.4 MT @ 7.4% Zn, 0.2% Cu, 2.6% Pb, 91 g/t Ag and 1.0 g/t Au
Production for 2012-2015 is listed in Table 10. As illustrated, mined zinc grades in 2015 were well above reserve grade and initial results for 2016 illustrate that zinc production is now trending down. Although the mine has been in operation for 80 years, I am uncertain about its future. There are ample reserves and resources but the ore haulage distance from the bottom of the mine to surface is exorbitant to say the least. Production during the period under assessment appears assured but beyond that it is a question mark. Table 11 illustrates my estimate of production to 2022.
MMG states that they have had a number of expressions of interest in this mine so I expect a sale of this asset shortly. It is typical that when a mine is down to its last five years or so of ore, the operation is sold by a big miner to a wannabe miner. The big miner extracts the remaining NPV without having to do any mining or rehabilitation work and the wannabe miner can now boast that they are actually a producer. So both backs are scratched.
Golden Grove is actually two separate mines a few kilometers apart: Gossan Hill and Scuddles. Information on these mines can be found in the Downloads section here .
In the case of the Gossan Hill mine, most zinc stopes are greater than 1,000 m deep and the ore must be hauled to surface by truck. This is likely a haul over 8 km on a ~15% ramp which would take a truck the better part of two hours for a round trip. At Scuddles, remaining zinc stopes are over 1,200 m deep and must be hauled up to approximately 700 m depth to the shaft loading pocket ( I assume this shaft is still operational). The long haulage distances are likely the production bottleneck. Table 12 illustrates 2012-2015 production figures. Note that these zinc grades are a combination of distinct copper and zinc zones so the grades listed are deceptively low. Copper rich and zinc rich zones are campaign milled separately and the portion of each zone milled annually varies.
Zinc rich reserves as of June 30, 2015 are:
2.0 MT @ 11.6% Zn, 0.4% Cu, 1,7% Pb 123 g/t Ag and 2.4 g/t Au
MMG announced recently that this mine is being “right sized” from 1.6 MT a year to 1.0 MT a year. This is likely tacit admission they can no longer get the more attractive ore at depth to surface quickly and what is near surface is uneconomic. Table 13 is my estimate of zinc production going forward assuming the zinc rich zones constitute 40% of annual mill feed. Against my better judgement I have assumed production continues to 2020 but this mine really is a tired dog that should be put out of its misery instead. This seldom happens though. Someone always comes along that thinks they know better.
MMG is currently constructing the Dugald River mine after an extensive test mining phase. This deposit is located in the Mt Isa area and was discovered well before my time in the area. Being predominantly zinc rich it attracted only scant attention from an area traditionally steeped in lead/silver mining. The Dugald River style of mineralisation is a sedimentary hosted base metal deposit. Mineralised widths vary from 3 m to 30 m. The mineralised zone extends approximately 2.4 km in strike length and up to 1.2 km down dip. The main Dugald lode is hosted within a major N-S striking steeply west dipping shear zone which cross cuts the strike of the Dugald River Slate stratigraphy at a low angle. Dip varies between 85° and 45° to the west. The mineralisation is open at depth. Blasthole open stoping will be used. Zinc recovery of 87.2% to a concentrate grading 51.6% Zn is expected. When I asked back in the 1980’s why this deposit was not being mined, a relatively high manganese content in the ore was one answer offered up. Smelters have issues with this.
Proven and probable reserves as of June 30, 2015 are:
22.1 MT @ 12.3% Zn, 2.0% Pb and 50 g/t Ag
Resources are greater than 56 MT at similar grades.
MMG expects to produce 1.7 MT or ore per annum with the ramp up commencing in mid-2018. Mill output at full production is expected to be 170,000 T of zinc in concentrate annually. It therefore represents Australia’s largest new zinc mine development and will be one of the top 10 in the world.
The investment decision was made by MMG based on their projection of the price of zinc increasing to the $1.75 /lb. range by 2017 and then sustaining $1.50/lb. for subsequent years. This is a price range I agree with since the zinc price will need to be attractive enough for a new suite of mines to justify development.
Table 14 is my estimate of the production ramp up. MMG has conducted an extensive test mining program here so I have no doubt that they will achieve this. It is a shame however that Mark Adams, my former boss at Mt. Isa is not leading this show up having left as General Manager of MMG’s Century mine last year when it closed. The beaches near Perth beckoned just like my golf clubs did I guess.
BHP rolled Cannington into South32 likely due to its limited economic mine life using BHP commodity price assumptions. The mine has predominantly been considered a silver/lead mine yet its zinc production has been very significant. Blasthole stoping is used to produce over 3 MT of ore annually. Table 15 illustrates FY2015 production and reserves remaining as of June 30, 2015. This is yet another mine in the prolific Mt. Isa region. This mine was a huge money maker for BHP during its prime.
The South32 Information Memorandum filed with the ASX here provides mining and milling details (page 1186 onwards) and the zinc production schedule reproduced in Table 16 through to ore exhaustion in 2023.
The resources (at a $90/t NSR) are roughly three times the reserve base. It is uncertain whether these resources are essentially sterilized by previous mining or readily accessible should it be decided to extend the mine life based on a rise in commodity prices. At one time BHP mulled open pit mining here at a 60% higher milling rate. By divesting of this asset to South32, I guess the ball is in their court now to determine whether they can convert resources into reserves. My suspicion is that the mine life will be much longer than illustrated in Table 16. For the geologists out there, there is a technical description of this type of deposit here . (Us mining engineers just want to know where the ore is.)
CBH Resources (Toho Zinc)
Toho acquired struggling CBH in 2010 apparently in order to internally source most of their concentrate requirements for a smelter in Japan.
This mine used to be called the Elura Mine and I had the opportunity to visit it in the early 1990’s. The orebody is now essentially mined out and only the mining of small stopes and remnants left in and around the previous mining areas is underway. Remnant mining can be very tricky business since it relies upon the good understanding of past activities, namely whether the previous mining areas nearby are backfilled adequately. High stress levels may also be present in some locations particularly sill pillars left between two previous mining levels.
Variations of blasthole stoping are being used and production has averaged in the 700,000 T a year rate over the past few years. The location of these remnants as of 2012 in relation to previous mining is illustrated below.
Toho Zinc does not publish mining performance details (in English at least) but a good sense of the operation can be obtained from the NI 43-101 filed by Coeur in 2013 (they have a silver royalty). Coeur also publishes annual mining production and reserve figures (for silver grade only unfortunately from which I infer a ~7% Zn head grade and 40,000 T a year zinc output). Based upon the reserve situation, it is inferred that this mine would close in roughly three years’ time. However, in February 2016 CBH announced here an 80% cut in production claiming weak commodity prices. CBH confirms that there are only 2-3 years of reserves left at previous production rates. I have assumed the mine returns to full production mid-2017 in Table 17 and the mine closes at the end of 2019. This may be overly optimistic.
Reference: Coeur NI 43-101 Endeavor Mine Technical Report, March 28, 2013. www.sedar.com
Old mining camps never die it seems. Broken Hill, New South Wales is a classic example of this. I bet there are some readers out there that have no clue what BHP stands for- Broken Hill Proprietorship. The Broken Hill mine was the cash cow that underpinned this mining empire. They had enough sense not to piss it away unlike most mining companies (but they are trying lately I guess). BHP was incorporated in 1885. Like Mt. Isa, Broken Hill was known as a silver/lead/zinc mine in that order of importance. The “Silver City”.
Charles Rasp is credited with the discovery of this deposit. The silver and lead rich portions were essentially mined out over one hundred years but there are a number of areas richer in zinc that are still exploited here. Unfortunately, I have been unable to find much information on current operations except to report that Toho expects to produce 34,000 T of zinc in concentrate annually and have not announced any alterations to plans.
The Rasp Mine mines remnants from the original BHP mine. The orebody is shaped like a boomerang as illustrated below. CBH mines remnants in the center and Perilya mines remnants currently in the Southern Operations. Both operations are classic swing producers that at times have lost considerable money and have been effectively subsidized by their Asian parent companies. This is one reason why zinc mining has been a crappy business more years than not for those that don’t have an owner with deep pockets or an extraordinarily rich orebody.
Perilya- Southern Operations
Perilya acquired assets on the north and south limb of Broken Hill in 2002. Zinc rich zones and remnants are mined currently on the south limb at what is known as the Southern Operations. From 2002-2010 over 15 MT of ore was mined with grades in the range of 6% Zn, 4% Pb plus silver. Perilya was caught up in the 2008 financial crisis like many mining companies. Shenzhen Zhongjin Lingnan Nonfemet Co. Ltd of China acquired 50.1% of the company in 2009 as a result. This was increased to 100% in 2013.
Following the financial crisis operations on the north limb (Potosi development and North Mine) were suspended and production levels were reduced 50%. Due to low prices and deteriorating ore quality, Perilya announced further job losses in March 2016 here. Production would be cut a further 30%. The mine apparently lost $A30M during the previous year due to low lead and zinc prices.
Since the owner is a private company that does not report annual results, I have had to do considerable reading between the lines. I assume 2015 production levels were roughly 900,000 t grading 6% Zn for 50,000 T of zinc in concentrate and going forward this will drop to 35,000 T per year to 2022. Predicting the actual outcome is a real crapshoot since production could rise on a price increase.
Perilya is a classic swing producer. At high commodity prices it would be possible to restart the Potosi development (1.6 MT @ 13.0% Zn, 3.1% Pb and 43 g/t Ag) and perhaps even the North Mine Deeps project (3.7 MT @ 11.3% Zn, 13.5% Pb and 219 g/t Ag).
When I worked in Queensland and the Northern Territory much of the mining action was actually in Western Australia, underground gold mining mostly. We looked upon that mining as real cowboy stuff. Undercapitalized, unsafe, real hand to mouth contract underground mining with little science applied. So I was pleasantly surprised to investigate Independence Group NL for this report. Here is a mining company that can actually develop new underground base metal mines cost effectively in Western Australia, turn a profit and pay their shareholders a dividend. A rare combination these days.
IGO owns the Jaguar Operation which is adjacent to the previous producing Teutonic Bore mine. The Jaguar and Bentley deposits are on strike with this mine. Jaguar is now mined out with all ore coming from the Bentley deposit. Significant copper, silver and gold quantities are also recovered. The life of Bentley is a bit of a mystery since it relies upon successful exploration down dip. Production for FY2016 and reserves as of June 30, 2015 are listed in Table 18. Production from FY2012 to FY2016 is illustrated in Table 19 along with my forecast to 2022 assuming 50% of the resource base is converted to reserves after depleting FY2016 mining from reserves. Reserves are inclusive of resources. IGO is currently drilling another nearby deposit, Triumph, but whether there is sufficient economic mineralization here or not is uncertain. I therefore illustrate the mine closing in 2019.
Aurelia Metals’ Hera mine provides another cautionary tale of accepting financing from Glencore. Mine startups seldom go according to plan and cash can quickly drain from the treasury. A poor startup here left the company in dire straits and Glencore attempted unsuccessfully to place the company into Administration. They have since kissed and made up.
This Cobar area deposit is somewhat unique in that most gold and silver can be liberated by gravity concentration and dore is poured on site. The mine also produces a bulk Pb/Zn concentrate containing precious metals but it is predominantly considered a gold mine currently. Blasthole stoping with ramp access is used. Table 20 illustrates FY 2016 reserves, resources and production figures.
Since annual zinc production is relatively minor I have assumed 9,000 T per year of zinc in concentrate through 2022 and that Aurelia will send Ivan a Christmas card annually.
Australian Zinc Mine Cost Competitiveness
Although the intent of this report is to look at total output potential for zinc, the question many likely have is what separates an economic deposit from an uneconomic deposit. I hope to have a spreadsheet based model shortly to help out but it should only be used in experienced hands with clear understanding of what concentrate precious metals report to in particular. The revenue side is only one aspect of the equation though.
Many of the miners assessed above have provided cost data or at least the cutoff Net Smelter Return (NSR) used to determine the threshold for differentiating between reserves (ore that covers site operating costs) and resources (mineralization that does not currently). These cutoff NSR’s can be used to provide a quick assessment of the viability of potential producers going forward. If a company is promoting their project but has an NSR below or near the cutoff of other similar deposits it is likely that this project requires a considerable sustainable increase in commodity prices. Table 21 summarizes the cutoff NSR’s used by some of the mines above. A new project would likely want an overall NSR at least 100% above the cutoff in order to cover the cost of mine construction, sustaining capital and other costs such as finance as well as to reward the long suffering owners (shareholders).
To give you some indication of what this means from a grade perspective, the Cannington cut-off NSR of $A120/t ore equates to an ore grade of 1.67% Zn, 1.36% Pb and 39 g/t Ag under their particular set of milling grades and recoveries, commodity pricing and exchange rate assumptions. So applying the 100% rule of thumb listed above suggests that grades of 6% Zn+Pb and 80 g/t Ag are likely the minimum grades possible for the development of a similar greenfield situation under these circumstances. I myself, would sleep better at night knowing my (underground) project was at least 10% Zn+Pb with some healthy silver credits. Obviously, having some payable copper and gold along for the ride greatly helps matters. This is a very crude way of looking at matters but at least it helps you focus on the better prospects. Below is how Rosebery determines the cutoff NSR annually for their reserve statements.
Summary of Australian Zinc Production
I have reproduced below my summary of Australian zinc mine output to 2022 assuming recent cutbacks at George Fisher, Lady Loretta and Endeavor are reversed in 2017. I assume McArthur River will remain at reduced production rates. With respect to new production only Stockman and perhaps Woodlawn and Triumph will be developed prior to 2022 but total production would likely not amount to more than 100,000 T zinc in concentrate by that time. I will discuss their prospects in a very brief module next. For those whose money is burning a hole in their pocket, here is an alternate source for information on some of these prospects. Pretty damn thin gruel on the exploration front due to lack of funding.
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