58. Ore Dilution Prediction – Its Always an Issue

mining reserve estimation
Over my years of preparing and reviewing mining studies, ore dilution often seems to be a contentious issue.  It is deemed either too low or too high, too optimistic or too pessimistic.  Everyone realizes that project studies can see significant economic impacts depending on what dilution factor is applied.  Hence we need to take the time to think about what dilution is being used and why.

Everyone has a preferred dilution method.

I have seen several different approaches for modelling and applying dilution.   Typically engineers and geologists seem to have their own personal favorites and tend to stick with them.   Here are some common dilution approaches.
1. Pick a Number:
This approach is quite simple.  Just pick a number that sounds appropriate for the orebody and the mining method.  There might not be any solid technical basis for the dilution value, but as long as it seems reasonable, it might go unchallenged.
2. SMU Compositing:
This approach takes each percent block (e.g.  a block is 20% waste and 80% ore) and mathematically composites it into a single Selective Mining Unit (“SMU”) block with an overall weighted average grade.  The SMU compositing process will incorporate some waste dilution into the block.  Possibly that could convert some ore blocks to waste once a cutoff grade is applied.   Some engineers may apply additional dilution beyond SMU compositing while others will consider the blocks fully diluted at the end of this step.
3. Diluting Envelope:
This approach assumes that a waste envelope surrounds the ore zone.  One estimates the volume of this waste envelope on different benches, assuming that it is mined with the ore.  The width of the waste envelope may be correlated to the blast hole spacing being used to define the ore and waste mining contacts.  The diluting grade within the waste envelope can be estimated or one may simply assume a more conservative zero-diluting grade.   In this approach, the average dilution factor can be applied to the final production schedule to arrive at the diluted tonnages and grades.  Alternatively, the individual diluted bench tonnes can be used for scheduling purposes.
4. Diluted Block Model:
This dilution approach uses complex logic to look at individual blocks in the block model, determine how many waste contact sides each block has, and then mathematically applies dilution based on the number of contacts.  Usually this approach relies on a direct swap of ore with waste.  If a block gains 100 m3 of waste, it must then lose 100 m3 of ore to maintain the volume balance.   The production schedule derived from the “diluted” block model usually requires no subsequent dilution factor.

When is the Cutoff Grade Applied?

Depending on which dilution approach is used, the cutoff grade will be applied either before or after dilution.   When dilution is being added to the final production schedule, then the cutoff grade will have been applied to the undiluted material (#1 and #2).
When dilution is incorporated into the block model itself (#3 and #4), then the cutoff grade is likely applied to the diluted blocks.   The timing of when to apply the cutoff grade will have an impact on the ore tonnes and had grade being reported.

Does one apply dilution in pit optimization?

Another occasion when dilution may be used is during pit optimization.  There are normally input fields for both a dilution factor and an ore loss factor.   Some engineers will apply dilution at this step while others will leave the factors at zero.  There are valid reasons for either approach.
My preference is use a zero dilution factor for optimization since the nature of the ore zones will be different at different revenue factors and hence dilution would be unique to each.   It would be good to verify the impact that the dilution factor has on your own pit optimization, otherwise it is simply being viewed as a contingency factor.

Conclusion

My personal experience is that, from a third party review perspective, reviewers tend to focus on the final dilution number used and whether it makes sense to them.   The actual approach used to arrive at that number tends to get less focus.
Regardless of which approach is being used, ensure that you can ultimately determine and quantify the percent dilution being applied.  This can be a bit more difficult with the mathematical block approaches.
Readers may yet have different dilution methods in their toolbox and I it would be interesting to share them.
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57. The Mining Bank or eBay for Mining Properties

mining properties
I recently attended the Money Show here in Toronto to learn a bit more about personal finanace, investing strategies, and to check out  the latest stock analysis software.
There was also a trade show, but only one mining company booth was present.  This definitely wasn’t the PDAC.  Interestingly there were about five marijuana company booths, so that is where the promotion is today.
The lone mining company was Globex Mining, here is their website.  They referred to themselves as a “mining bank”, so that was something that peaked my interest.

Mining bank

Speaking with their president, Jack Stoch, he gave me an overview on their business model.  As I understood it, GLOBEX’s model is to acquire a portfolio of mineral properties.  They would try to enhance their value by undertaking some limited geological work.  Finally they would option, JV, or sell the property while retaining an NSR royalty.
Mr. Stoch told me that Globex currently has over 140 land packages in their inventory.  Their properties will be at different stages.  Some have resource estimates, others only mineralized drill intersections, mineral showings, untested geophysical targets, or combinations of these.
They are focusing their acquisitions on lower risk jurisdictions like Quebec, Ontario, Nova Scotia, New Brunswick, Tennessee, Nevada, Washington, and Germany.  They try to acquire historical mines that have old shafts, following the adage the best place to find a new mine is next to an old mine.   They also have some industrial mineral properties.

 

Globex’s only NSR revenue property right now is a zinc project in Tennessee that can generate a seven-figure royalty each year, when that operation is up and running.  Unfortunately for Globex the zinc operation has not been in consistent operation the last few years.

Its a good concept

I like the concept that Globex are promoting.  I like the idea of having a one-stop shop that acquires and options out exploration properties to mining companies looking for new projects.
I also like the idea of trying to consolidate land packages in an area,  minimizing the patchwork of multiple ownership claims that can hinder advanced development.
Globex hope that by putting time and effort into a bunch of properties a few of them will pay off.  If they can generate sufficient NSR revenues, the company may get to the self-sustaining stage.

Its not a new idea

The idea of companies involving themselves in a portfolio of early stage prospects isn’t new.  This has been being done by EMX Royalty Corp (formerly Eurasian Minerals) for properties around the globe.    Abitibi Royalties is also doing something vaguely similar, whereby they would help fund prospectors in exchange for a long term royalty on a property. There are likely others.
There is a high risk to being successful but the cost of entry is relatively low.
It will be interesting to watch Globex over the longer term to see how many properties they can acquire and how many of these will pay off. Spending a bit of money on mapping and exploration on a property may benefit them by increasing value in the eyes of potential partners.
Statistically, mineral exploration is a high risk game but by limiting expenditures and diversifying the portfolio, some of that risk can be mitigated.
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55. Underground Feasibility Forecasts vs Actuals

underground costing
I recently attended a CIM Management and Economics Society presentation here in Toronto discussing the differences between actual underground production versus the forecast used in the feasibility study. The presenter was Paul Tim Whillans from Vancouver Canada.
His topic is interesting and relevant to today’s mining industry.  Paul raised many thoughtful points supported by data. He gave me permission to share his information.
The abstract for his paper is inerted below.  The paper can be downloaded at this LINK and here are the presentation slides.

ABSTRACT

An underground mining study that is done in accordance with NI43-101, JORC or similar reporting code is generally assumed by the public to be representative, independent and impartial. However, it has been well documented by academics and professionals in our industry that there is a sharp difference between the forecasts presented in these underground studies and the actual costs when a mine is put into production.
For underground mines, the risks associated with obtaining representative information are much greater than for surface mining and the cost of accessing underground ore is also proportionally much greater. There is a pressing need to align expectations, by improving the accuracy of projections. This will result in reduced risk to mining companies and investors and provide more reliable information to government agencies, the public, and more importantly, the communities in which the proposed mine will operate.
The objective of this article and an article currently being written titled “Mining Dilution and Mineral Losses” is to:
– Discuss the dynamics of intention that lead to over-optimism;
– Provide simple tools to identify which studies are likely to be more closely aligned with reality;
– Identify some specific points where underground mining studies are generally weak;
– Discuss practices currently in use in our industry that lead to a composite or aggregate effect of over optimism;
– Describe the effects of overly optimistic studies;
– Outline specific changes that are necessary to overcome these challenges; and
– Stimulate discussion and awareness that will lead to better standards.”

Conclusion

I agree with many of the points raised by Paul in his study. The mining industry has some credibility issues based on recent performance and therefore understanding the causes and then repairing that credibility will be important for the future.
Credibility ultimately impacts on shareholder returns, government returns, local community benefits, and worker health and safety; so having a well designed mine will realize benefits for many parties.
If you need more information Paul’s website is at http://www.whillansminestudies.com/
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53. Ore Stockpiling – Why are we doing this again?

ore stockpile
In many of the past mining studies that I have worked, stockpiling strategies were discussed and usually implemented. However sometimes team members were surprised at the size of the stockpiles that were generated by the production plan. In some cases it was apparent that not all team members were clear on the purpose of  stockpiling or had preconceived ideas on the rationale behind it. To many stockpiling may seem like a good idea until they saw it in action.
Mine Stockpile
In this blog I won’t go into all the costs and environmental issues associated with stockpile operation.  The discussion focuses on the reasons for stockpiling and why stockpiles can get large in size or numerous in quantity.
In my experience there are four main reasons why ore stockpiling might be done. They are:
1. Campaigning: For metallurgical reasons if there are some ore types that can cause process difficulties if mixed  with other ores. The problematic ore might be stockpiled until sufficient inventory allows one to process that ore (i.e. campaign) through the mill. Such stockpiles will only grow as large as the operator allows them to grow. At any time the operator can process the material and deplete the stockpile. Be aware that mining operations might still be mining other ore types, then those ores may need to be stockpiled during the campaigning.  That means even more ore stockpiles at site.
2. Grade Optimization: This stockpiling approach is used in situations where the mine delivers more ore than is required by the plant, thereby allowing the best grades to be processed directly while lower grades are stockpiled for a future date. Possibly one or more grade stockpiles may be used, for example a low grade and a medium-low grade stockpile. Such stockpiles may not get processed for years, possibly until the mine is depleted or until the mined grades are lower than those in the stockpile. Such stockpiles can grow to enormous size if accumulated over many years.  Oxidation and processability may be a concern with long term stockpiles.
3. Surge Control: Surge piles may be used in cases where the mine may have a fluctuating ore delivery rate and on some days excess ore is produced while other days there is underproduction. The stockpile is simply used to make up the difference to the plant to provide a steady feed rate. These stockpiles are also available as short term emergency supply if for some reason the mine is shut down (e.g. extreme weather). In general such stockpiles may be relatively small in size since they are simply used for surge control.
4. Blending: Blending stockpiles may be used where a processing plant needs a certain quality of feed material with respect to head grade or contaminant ratios (silica, iron, etc.). Blending stockpiles enables the operator to ensure the plant feed quality to be within a consistent range. Such stockpiles may not be large individually; however there could be several of them depending on the nature of the orebody.
There may be other stockpiling strategies beyond the four listed above but those are the most common.

Test Stockpiling Strategies

Using today’s production scheduling software, one can test multiple stockpiling strategies by applying different cutoff grades or using multiple grade stockpiles. The scheduling software algorithms determine whether one should be adding to stockpile or reclaiming from it. The software will track grades in the stockpile and sometimes be able to model stockpile balances assuming reclaim by average grade, or first in-first out (FIFO), or last in-first out (LIFO).
ore stockpile
Stockpiling in most cases provides potential benefits to an operation and the project economics. Even if metallurgical blending or ore campaigning is not required, one should always test the project economics with a few grade stockpiling scenarios.
Unfortunately these are not simple to undertake when using a manual scheduling approach and so are a reason to move towards automated scheduling software.
Make sure everyone on the team understands the rationale for the stockpiling strategy and what the stockpiles might ultimately look like. They might be surprised.
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52. Mining Press Releases – Where to Get Them

mining news
There are a lot of sources of mining information on the internet.  These encompass topics such as technical articles, analyst opinions, and company press releases. If your interest is largely company news releases, what is the best way to get these?
One way is to go to the individual company website and sign-up one their mailing list. This approach generally works well but it forces you to sign up on a myriad of websites if you intend to follow a lot of companies.

There are alternatives

One option is to sign-up for a free account with a newswire service where you can select specific companies to follow.  You will get emailed news releases as soon as they are disseminated. The nice thing here is that you can select mining companies, non-mining public companies, as well as entire industries. Here are some that I personally use.
Marketwire: There you can create a “Hot Off the Wire” account and then select your companies of interest. You can also select entire industries to add to your company list.
CNW Group Ltd.  Create an account at Cision and search various companies to add to your “My Subscriptions” list.Junior Mining News screenshot
Junior Mining News is another source to get general news updates via their daily newsletter (see screenshot). Their daily email gives a brief summary of today’s news events and includes “Read More..” links if you want the entire press release. This website accesses some of the same news release distributors as mentioned above so there could be some repetition from time to time.

Its easy

Using the services described above, it’s easy to sign up for multiple companies, too many companies in fact. Its easy to get inundated with emails.
Public companies need to keep an active news flow  and some companies are very good at it.
By using the press release distribution websites you are consolidating your requests, thereby making it easier to control the amount of information you want to receive.
Feel free to share your method for tracking companies, whether using some of the same services or something entirely different.
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51. Pre-Concentration – Savior or Not?

pre-concentration
Can pre-concentration become a savior for the mining industry by lowering metal production costs?
Pre-concentration is a way of reducing the quantity of ore requiring higher cost downstream processing, i.e. grinding in particular.  One can attain significant cost savings in energy consumption and operating expenses by using a low cost method to pre-concentrate minerals into a smaller volume. A previous blog “Remote Sensing of Ore Grades” discussed one new pre-concentration method currently under development.

Pre-concentration isn’t new

Pre-concentration has been around for many years.  However the techniques available are generally limited.  Hence many ore types are not amenable to it..unfortunately.
The main methods available are:
Ore sorting, which can be done using automated optical, electrical, or magnetic susceptibility sensors to separate ore particles from waste. The different sensors can rely on colour recognition, near infrared radiation, x-ray fluorescence, x-ray transmission, radiometric, or electromagnetic properties. The sensors can determine if a particle contains valuable mineral or waste, thereby sending a signal to activate air jets to deflect material into ore and waste bins.
Density separation, or specific gravity differences are another property that some pre-concentration methods can use. Gravity based systems such as dense media separation (DMS), jigs, or centrifugal concentrators are currently in commercial production.
Scrubbing, another very simple pre-concentration method is scrubbing, whereby simply separating fines or coatings may remove deleterious materials prior to final processing.

 BenefitsJig Plant 1

Pre-concentration provides several benefits:
  • If done underground or at satellite mine site, the ore hoisting or ore transport costs can be reduced.
  • If the pre-concentration rejects can be used as mine backfill, this can reduce backfilling costs.
  • Processing of higher grade pre-concentrated mill feed can reduce energy costs and ultimately reduce the cash cost of metal produced.
  • Grinding costs can be reduced if waste particles are harder than the ore particles and they can be scalped.
  • Minimizing waste through the process plant will reduce the quantity of fine tailings that must be disposed of.
  • Lowering operating costs may potentially allow lowering of the cutoff grade and increasing mineral reserves.
  • Higher head grades would increase metal production without needing an increase in plant throughput.

Limited ore types are suited for pre-concentration

Not all ore types are amenable to pre-concentration and therefore a rigorous testing program is required. In most cases a pre-con method is relatively obvious to metallurgical engineers but testing is still required to measure performance.
Testing is required to determine the waste rejection achieved without incurring significant ore loss. Generally one can produce a higher quality product if one is willing to reject more ore with the waste.  It becomes a trade-off of metal recovery versus processing cost savings.
Fine particles generated in the crushing stage might need to bypass the pre-con circuit. If this bypassed material is sent to downstream processing circuits, one may need to examine crushers that minimize fines to avoid excessive material bypassing the pre-con circuit.

Reject waste or reject ore?

One must decide if the pre-con system should reject waste particles from the material stream or reject ore particles from the stream.  The overall metal recovery and product quality may be impacted depending on which approach is used.

Conclusion

The bottom line is that the mining industry is continually looking for ways to improve costs and pre-concentration may be a great way to do this.   Every process plant design should take a look at it to see if is feasible for their ore type.
While the existing pre-concentration methods have their limitations, future technologies may bring in more ways to pre-concentrate.  This is probably an area where research dollars would be well spent.
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48. Online Collaboration and Management Tools (Part 2)

networking
This blog is the Part 2 continuation of a prior post regarding collaboration software tools that mining teams should consider.   Here are a few more ideas I’d like to share, having found that these are great to have in your toolbox.
G-suite and miningG-Suite: is the family of Google Drive, Docs, Sheets, and Slides online services.
Group collaboration can be frustrating using spreadsheets or text documents.  We typically end up with different versions of the same document floating around.  No one is sure whether they are editing the most recent version or which version they should be editing.
With G-Suite (Google Sheets and Google Docs) you can create online spreadsheets and documents and allow multiple team members to review and edit them in real-time online at the same time.
Writing reports gets simpler since there is only one working version of the document. A “track changes” option is there (called “Suggesting”) and everyone can see the edits as they are being made. No more asking “who has the most current version?”  This type of collaborative editing is also great for Design Criteria Documents that are regularly being updated by different team members.
I have used both DropBox and Google Drive, but my preference is using Google Drive since it integrates well with G-Suite.

Foxit Reader:  This is an alternative to Adobe Reader and can be used for reviewing PDF documents, whether text documents or drawings.
Foxit provides great editing and commenting tools like highlighting text, adding comments, drawing lines and boxes, adding comment balloons, cut & pasting images into the PDF file, and then saving the commented version.
For the most part I have stopped using Adobe Reader and have now switched over to Foxit due to commenting capability that it provides.
Google Hangouts:  This is an online and mobile application for team conference calling.  It allows screen sharing, online group video conversations, sends out meeting reminders, and it will call participants at the require time.
While Hangouts has many of the same features as Skype, it integrates with Google Calendar and Gmail.   Most of the tech world uses Hangouts instead of Skype, but I’m not sure if the mining industry is ready to move away from Skype.
An honorable mention for video-conferencing goes to Zoom. Some tech developers have been switching to Zoom, they feel it has more capabilities than Hangouts and better video resolution. I have never used it however.

Other Software

Those are a few of the software tools that I have found useful and so now you’re probably wondering “what else is out there for me?” The website The Freelance Stack lists many of different tools that exist. Check them out and some of the others may be of value to you. :

Geology & Mining Software

One of the standard marketing approaches used by tech software is to provide a fully functional product for free and then charge money to access the enhanced features. The goal is to get future users familiarized and trained on the product.  They hope that they will get hooked on the product and decide to upgrade their plan for the full product suite.
I’m not sure whether any geology or mining software  is available for free in a fully functional format with optional upgrading. By functional, I don’t mean simply providing a “viewer” to view the work of others or a 30-day free trial period.  I mean actual software that provides some useful capability for free in order to get you hooked. Please let us know if this software marketing approach exists in the mining industry.

Conclusion

The bottom line is that there is a lot of interesting collaboration software out there.  Its readily available, much of it is free, and can make managing your remote project teams easier. Just because the software is used by the tech industry and millennials, don’t assume it won’t have a benefit to the mining industry.
The downside is the need to train and learn the new software, and the mining industry may not be so receptive to that.
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47. Online Collaboration and Management Tools (Part 1)

networking
Update:  This blog was originally published March 2016.   However like all things, the online world keeps evolving. So I have updated Part 1 and Part 2 of the blog (Dec 2018).  I added new software suggestions and removed some.
As part of a side business, I have been working alongside a team of software developers. It has been a good learning experience for me to see how the tech world does things compared to how the mining industry likes to work. We see a lot of private equity flowing into tech and less into mining, so they must be doing something right.
The tech start-up industry has developed its own set of jargon.  Common terms are agile management, lean start-ups, disruption, minimum viable products, pings, fail fast, and sprints.
Some of their work approaches do not make sense for the mining industry where one doesn’t have the luxury of using trial-and-error and customer feedback to help complete a project.
For software, the attitude is get it out the door fast and your customers will then tell you what fixes are needed. In mining you want to get it right the first time.  Having said that, some mining people will say they have seen 43-101 technical reports that follow the “wait for customer feedback” model.
Now where the tech industry can provide us with some guidance is in the implementation of collaboration tools. It is becoming more common for software developers to work remotely.  To collaborate they use the technology available or they develop new technology to meet their needs.  Mining teams are also working more and more from remote offices these days.

What are the collaboration software available

The following is a partial list (Part 1) of free software tools that I have used, mainly because I was forced to. With some hesitation at first, I have subsequently found the tools easy to use.  Many of them can definitely be applied in the mining industry with remote and diverse study teams.
There are a lot more tech tools out there but my list includes some that I have personally used. Most of these are free to begin with, and enhanced features are available at a minimal cost. However even the free versions are functional and can be used to build a comfort level in the team. Most of them provide both web based access and mobile access so even when you’re on the road you can still use them and contribute.

Trello

Trello: If you want to create a “to-do list” or task list for your team, this is the software to use. Imagine a bunch of  post-it notes that you can place under different categories, assign persons to each note, attached a file to the note if you wish, and then have back and forth discussions within each note.   Once a task is done, just drag the note to another category (e.g. “In Progress”, “Completed”). Anyone on the team can be invited to the Trello Board and can collaborate. See the image below for an example Trello screenshot.   This is a great tool for helping to manage tasks in a mining study.

 

Trello screenshot

Slack

Slack: If you want to maintain a running dialogue of group discussions that invited team members can follow and join in on, then Slack (a Canadian company) is for you. It can replace the long confusing back-and-forth emails that we commonly see.  If someone forgets to “reply all” the rest of the team is out of the loop. See the image below for an example Slack screenshot. It’s great for discussions among the team.  You can also have private one-on-one discussions or wide open team discussions.  You can attach files too and you can get pinged when something new is added. It provides permanent record of conversations and decisions.

Slack Screenshot

Mural

Mural:  Mural is a recent innovation to solve the issue that remote teams have of not sitting in the same room and writing ideas down on a whiteboard.   For that last while, there was no good white boarding software out there but I understand that Mural fills the gap.  i have not used it so cannot vouch for its simplicity, however it seems to be catching with the tech developers.  The screenshot below shows the type of inter-actions possble.  Each person has access to write on the whiteboard.
Basecamp: is similar program to Slack that incorporates features from both the above and some people swear by this tool. I have not personally used it so cannot vouch for it, but some say it is very good.

Conclusion

The bottom line is that there is a lot of good stuff out there, readily available, much of it free, and can facilitate collaboration among your teams. Just because its tech industry related, don’t assume it wouldn’t have an application in the mining world.  As millennials enter the mining workforce, these tools may gain a foothold.
To read about even more collaborative tools, take a look at Part 2 of this blog.  Comments on any of the discussions or software are appreciated.
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46. Tailings Disposal Method Risk

mine tailings
After the Mt Polley and Samarco tailings failures, there have been ongoing discussions about the benefits of filtered (dry stack) tailings as the only way to eliminate the risk of catastrophic failure. Mining companies would all like to see risk reductions at their projects.

Filtered tailings stack

However what mining companies don’t like to see are the capital and operating costs associated with dry stacking. The filtering cost and tailings transport cost are both higher than for conventional tailings disposal. Obviously this cost increase gets offset against improved environmental risk and simpler closure.

So what is a company to do?

In my experience when designing a new mining project, all companies at some point complete a trade-off study for different tailings disposal methods and disposal sites. Contrary to some environmental narratives, mining companies really do want to know about their different tailings options.  They would all adopt the dry stack approach if it was the most advantageous method.
The mining companies are fully aware of the benefits but the dilemma is the cost and being able to somehow justify the technology. Complicating their decision, companies also have other options for reducing their tailings risk.

The  final decision can get complex.

In a tailings risk analysis, people will use a risk-weighting approach to assign an expected economic impact to their tailings plans. For example, if the cost of a failure is $200 million and the risk is 0.1%, then the Expected Cost is $200,000. The problem with this is its based on a theoretical calculation on an assumed likelihood of failure.   In reality either the dam will fail or it won’t.  So failure remediation money will be spent ($200M) or it won’t be spent ($zero), it won’t be partially spent ($200k).
The accepted tailings risk therefore becomes a subjective factor.
While implementing a dry stack may reduce the risk of catastrophic failure to near zero, implementing a $100,000 per year monitoring program on a conventional tailings pond will reduce its risk.
Implementing a $500,000 per year monitoring program would reduce that risk even further.
Installing in a water treatment plant to enable periodic water releases may further lower the tailings risk.
The company can look at various mitigation options to keep lowering their risk, although none of the options would necessarily bring the risk down to zero. Ultimately the company could compare the various risk mitigation options against the dry stack costs in order to arrive at an optimal path forward.

What level of risk is acceptable?

So the question ultimately becomes how low does one need to reduce the tailings risk before it is acceptable to shareholders, regulators, and the public. I don’t think the answer is that one must lower the risk down to zero. There are not many things in today’s world that have zero risk. Driving a car, air travel, shipping oil by ocean tanker, having a gas furnace in your house..none of these have zero risk yet we accept them as part of living.
Environmental groups continually discuss ways of forcing regulators and mining companies to take action against the risk of tailings failure. This is commendable.
However they generally fail to provide any guidance on what level of risk would be acceptable to them or to the public. It seems to be difficult for these groups to define what an acceptable risk is. They offer no solutions, other than either zero risk or shut down all mining.

Conclusion

We know that mining is here to stay so we all should work together towards solutions.
The solutions need to be realistic in order to be taken seriously and to play a real role in redefining tailings disposal. Dry stack may not be the only solution and we should be looking for more ways to improve tailings disposal.
Since these other options don’t seem to be available yet, dry stack tends to offer the best solution in most circumstances.  I have written another blog on this topic “Fluid Tailings – Time to Kick The Habit?”
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44. Higher Metal Prices – Should We Lower the Cut-Off Grade?

When metals prices are high, we are generally told that we should lower the cutoff grade. Our cutoff grade versus metal price formula tells us this is the correct thing do. Our grade-tonnage curve reaffirms this since we will now have more ounces of gold in the mineral reserve.

But is lowering the cutoff grade really the right thing to do?

Books have been written on the subject of cutoff grades where readers can get all kinds of detailed logic and calculations using Greek symbols (F = δV* − dV*/dT). Here is one well known book by Ken Lane, available on Amazon HERE.
Recently we have seen a trend of higher cash costs at operating mines when commodity prices are high. Why is this?
It may be due to higher cost operating inputs due to increasing labour rates or supplies. It may also be partly due to the lowering of cutoff grades.  This lowers the head grade, which then requires more tonnes to be milled to produce the same quantity of metal.
A mining construction manager once said to me that he never understood us mining guys who lower the cutoff grade when gold prices increase. His concern was that since the plant throughput rate is fixed, when gold prices are high we suddenly decide to lower the head grade and produce fewer and higher cost ounces of gold.

Do the opposite

His point was that we should do the opposite.  When prices are high, we should produce more ounces of gold, not fewer. In essence, periods when supply is low (or demand is high) may not be the right time to further cut  supply by lowering head grades.
Now this is the point where the grade-tonnage curve comes into play.
Certainly one can lower the cutoff grade, lower the head grade and produce fewer ounces of gold.  The upside being an extension in the mine life.  A company can report more ounces in reserves and perhaps the overall image of the company looks better (if it is being valued on reserves).

What if metal prices drop back?

The problem is that there is no guarantee that metal prices will remain where they are and the new lower cutoff grade will remain where it is. If the metal prices drop back down, the cutoff grade will be increased and the mineral reserve will revert back to where it was. All that was really done was accept a year of lower metal production for no real long term benefit.
This trade-off  contrasts a short term vision (i.e. maximizing annual production) against a long term vision (i.e. extending mineral reserves).

Conclusion

The bottom line is that there is no simple answer on what to do with the cutoff grades.  Hence there is a need to write books about it.
Different companies have different corporate objectives and each mining project will be unique with regards to the impacts of cutoff grade changes on the orebody.
I would like to caution that one should be mindful when plugging in new metal prices, and then running off to the mine operations department with the new cutoff grade. One should fully understand both the long term and short term impacts of that decision.
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42. Global Tax Regimes – How Do They Compare?

mining economics
Update: This blog was originally written in Feb 2016, but has been updated in Dec 2018.
As a reminder for all QP’s doing economic analysis for PEA’s, don’t forget that one needs to present the economic results on an after-tax basis.
Every once in a while I still see PEA technical reports issued with only pre-tax financials.  That report is likely to get red- flagged by the securities regulators.  The company will need to amend their press release and technical report  to provide the after tax results.    No harm done other than some red faces.

Taxes can be complicated

When doing a tax calculation in your model, where can you find international tax information?  PWC has a very useful tax-related website.  The weblink below was sent to me by one of my industry colleagues and I thought it would be good to share it.
The PWC micro-site provides a host of tax and royalty information for selected countries.  The page is located at http://www.pwc.com/gx/en/industries/energy-utilities-mining/mining/tax.html
On the site they have a searchable database for tax information for specific countries.
The PWC tax and financial information includes topics such as:
  • Corporate tax rates
  • Excess profits taxes
  • Mineral taxes for different commodities
  • Mineral royalties
  • Rates of permissible amortization
  • VAT and other regulated payments
  • Export taxes
  • Withholding taxes
  • Fiscal stability agreements
  • Social contribution requirements
PWC has a great web site and hopefully they will keep the information up to date since tax changes happen constantly.   It would be nice to see them add more countries to their 23 country database but it’s already good.  Check it out.

 

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41. Resource Estimates – Are Independent Audits A Good Idea?

mining reserves
Question: How important is the integrity of a tailings dam to the successful operation of a mine?
Answer: Very important.
Tailings dam stability is so important that in some jurisdictions regulators may be requiring that mining companies have third party independent review boards or third party audits done on their tailings dams.  The feeling is that, although a reputable consultant may be doing the dam design, there is still a need for some outside oversight.
Differences in interpretation, experience, or errors of omission are a possibility regardless of who does the design.  Hence a second set of eyes can be beneficial.

Is the resource estimate important?

Next question is how important is the integrity of the resource and reserve estimate to the successful operation of a mine?
Answer: Very important.  The mine life, project economics, and shareholder value all rely on it.     So why aren’t a second set of eyes or third party audits very common?

NI 43-101 was the first step

In the years prior to 43-101, junior mining companies could produce their own resource estimates and disclose the results publicly.  With the advent of NI 43-101, a second set of eyes was introduced whereby an independent QP  could review the company’s internal resource and/or prepare their own estimate.  Now the QP ultimately takes legal responsible for the estimate.
Nowadays most small companies do not develop their own in-house resource estimates.  The task is generally awarded to an independent QP.

Resource estimation is a special skill

Possibly companies don’t prepare their own resource estimates due to the specialization needed in modelling and geostatistics. Maybe its due to the skills needed to operate block modeling software.   Maybe the companies feel that doing their own internal resource estimate is a waste of time since an independent QP will be doing the work anyway.

The QP is the final answer..or is it?

Currently it seems the project resource estimate is prepared solely by the QP or a team of QP’s.   In most cases this resource gets published without any other oversight. In other words no second set of eyes has taken a look at it.  We assume the QP is a qualified expert, their judgement is without question, and their work is error free.

Leapfrog Model

As we have seen, some resources estimates have been mishandled and disciplinary actions have been taken against QP’s.   The conclusion is that not all QP’s are perfect.
Just because someone meets the requirements to be a Competent Person or a Qualified Person does not automatically mean they are competent or qualified. Geological modeling is not an exact science and will be based on their personal experience.

What is good practice?

The question being asked is whether it would be good practice for companies to have a second set of eyes take a look at their resource estimates developed by independent QP’s?
Where I have been involved in due diligence for acquisitions or mergers, it is not uncommon for one side to rebuild the resource model with their own technical team.  They don’t have 100% confidence in the original resource handed over to them.   The first thing asked is for the drill hole database.
One downside to a third party review is the added cost to the owner.
Another downside is that when one consultant reviews another consultant’s work there is a tendency to have a list of concerns. Some of these may not be material, which then muddles the conclusion of the review.
On the positive side, a third party review may identify serious interpretation issues or judgement decisions that could be fatal to the resource.
If tailings dams are so important that they require a second set of eyes, why not the resource estimate?  After all, it is the foundation of it all.
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