64. Is Insitu Leaching the “Green Mining” Future

It is no surprise to anyone that permitting new open pit mines in today’s environment is getting more difficult and even impossible in some areas.   Underground mines also have their challenges, permitting as well as requiring relatively high grades to be economic.
So where might our future metal supplies come from?  What are the options?

Insitu leaching may be the answer

I recently came across an insitu leaching website, called BIOMore.  This was an initiative sponsored by the EU that looked at insitu leaching technology for metal recovery.    Environmental issues associated with mining in Europe, particularly open pit mining, raised concerns about how ore bodies in the EU might be developed in the future.
Insitu leaching technology was viewed as playing an important role.  This is due to its minimal surface disturbance, ability to operate at great depth, and its potential in urban and developed locations.  Sounds like a nice solution to have on hand.
The EU-funded BIOMOre research project was completed in 2018.  It was designed to develop a new technological framework for the insitu recovering of metals from deep deposits.  The process would rely on controlled stimulation of pre-existing fractures in combination with insitu bio-leaching.  The study mainly focused on the application of existing technologies.

Fracing will be an issue

Insitu leaching essentially relies on exposing mineralized surfaces to leach solutions.  This may require hydro-fracturing (fracing) to enhance insitu bio-leaching using bacteria and acid.   Fracing is currently banned in some European countries so this is going to be a potential issue.  From a leaching perspective, the trade-off would be between no fracing, reduced cost & lower metal recovery against higher cost & higher metal recovery with fracing.
If insitu leaching technology development is successful, it could help exploit European base metals from porphyry deposits (Cu, Au, Mo, Cu, REE, PGE, Re, Pb, Cu, Pt, Au) and other gold and uranium deposits.   Insitu leaching would avoid building a mine, mine infrastructure, and it generates almost no tailings nor waste dumps.  Leaching is expected to be cheaper than traditional mining and more acceptable to the public. Insitu leaching is being touted as “Green Mining”

What did they conclude

This study deliverables included comprehensive documentation, an economic evaluation, and risk analysis of a potential insitu bio-leaching operation.  The basis was a theoretical deposit, looking at different well field set-ups.
The study concluded that accessing potential deposits at depths of around 1000 m is economically feasible only if curved wells are used.  The most relevant operational parameters are sufficient permeability in the ore zone and an adequate contact surface between the ore and leaching solution.   The depth of the deposit is indirectly relevant, but more importantly the well installation cost per volume of deposit is critical.  Hence curved wells are optimal.
One interesting suggestion was combining an insitu leach operation with geothermal energy recovery.  This might result in additional project revenue stream with only a marginal cost increase.
It was suggested that insitu leach operations might be attractive in former mining regions where high grade deposits have been mined out yet nearby low grade deposits are well defined. Social license for insitu leaching may also be more accepting in these areas.
If you are interested in learning more about insitu leaching technology and the chemistry aspect, the BIOMore study deliverables are available for downloading at this site.
In the past, mining engineers like myself were told to learn the basics of crushing, grinding, and flotation to become more well rounded.  I may suggest that future mining engineers may need to learn the basics of directional drilling, hydro-fracing, and chemistry.  Sounds like petroleum engineering.

Some aspects are still uncertain

In practical terms, some things are still not clear to me. For example are how much effort and diligence must go into properly characterizing the permeability of a rock mass.  As well, how complex a task is it to metallurgically characterize the deposit spatially with regards to it being amenable to insitu leaching.  Not all ore types will behave the same and be amenable to leaching.
I am also curious about the ability to finance such projects, given the caution associated with any novel technology.  Many financiers prefer projects that rely on proven and conventional operating methods.
Notwithstanding those concerns, likely insitu leaching technology will continue to advance and show even more promise, and eventually gain greater acceptance.
While some innovators are looking at new ways to drill, blast, and move rock, the real innovators are looking at ways to recover metals without moving any rock at all.
For those interested, Excelsior Mining is looking to open a copper oxide insitu leaching operation in Arizona.  Here is video of how their technology will work.
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62. AI versus the Geologists

We likely have all seen recent articles about how Artificial Intelligence (AI) is going to change the mining industry.   I have been wondering if AI is a real solution or just a great buzzword.   My original skepticism has diminished somewhat and let me explain why.
At a booth at the 2019 PDAC I had a chance to speak with a publicly traded company called Albert Mining (referencing Albert Einstein’s intelligence).  They are providing exploration consulting services by applying a form of AI and have been doing so for many years.  The company has been around since 2005 but were not using the term AI to describe their methods.
These days the term “AI” has become very trendy.  Currently IBM Canada and Goldcorp are using Watson and AI to further their exploration efforts on the Red Lake property. GoldSpot Discoveries is another recent player in the mining AI field.  It appears Goldspot offers something similar to Albert Mining but they extend their platform to include picking projects, picking teams, and picking investments. That’s a lot of analysis to undertake.  Albert Mining is focused solely on mineral exploration.

Here is what I learned

Albert Mining’s system, called CARDS (Computer Aided Resource Detection System) uses pattern recognition and multi-variate analysis to examine a mineral property to look for targets.     The system requires that the property has some known mineralization hits and assay samples.  These are used to “teach” the software.   Both positive hits and negative hits are valuable in this teaching step.
The exploration property is sub-divided into cells and data are assigned to each cell.  These data attributes could be derived from geophysics, geochemistry, topography, soil samples, indicator minerals, assayed samples, geological maps, etc.  I was told that a cell could contain over 700 different data attributes.
The algorithm then examines the cell data to teach itself which attributes correlate to known mineralization and which attributes correlate with barren areas. It essentially determines a geological “signature” for each mineralization type.    There could be millions of data points and combinations of attributes.  Correlation patterns may be invisible to the naked eye, but not to the computer algorithm.
Once the geological signatures are determined, the remainder of the property is examined to look for similar signature hits.  Geological biases are eliminated since it is all data driven.   The newly defined exploration targets are given a ranking score based on the extent of correlation.
Some things to note are that the system works best for shallow deposits, unless one has some deep penetrating geophysical surveys.  The system works best if there is fairly uniform data coverage across the entire property.  The property should also have generally similar geological conditions and as mentioned before, the property needs to have some mineralized assay information.
This exploration approach reminds me somewhat of the book Moneyball.  This book is about the Oakland A’s baseball team where unconventional statistics were used to rank players in order to find hidden gems.

Are geologists becoming obsolete?

I was told that many in the geological community tend to discount the AI approach.  Either they don’t think it will work or they are fearing for their jobs.  Personally I don’t understand these fears nor can I really see how geologists can ever be eliminated.  Someone still has to collect and prepare the data as well as ultimately make the final decision on the proposed targets.   I don’t see the downside in using AI as another tool in the geologist’s toolbox.
Albert Mining’s stock price has recently gained some traction (note: I am not promoting them)  because junior mining news releases are starting to mention their name more often (Spruce Ridge Resources and Falco Resources are some examples).
Probably years ago if a mining company said their drill targets were generated by an algorithm, they might have gotten strange looks.   Today if a mining company says their drill targets were generated by AI, it gives them a cutting edge persona.  Times have changed.

In conclusion

I suggest we all take a closer looks at the AI technology to better understand what it does.
P.S. I  might also suggest that Albert Mining consider revising their company name to incorporate the term “AI” to stay on trend.
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61. Ore Dilution – An Underground Perspective

A few months ago I wrote a blog about different approaches that mining engineers are using to predict dilution in an open pit setting. You can read the blog at this link. Since that time I have been in touch with the author of a technical paper on dilution specifically related to underground operations. Given that my previous blog was from an open pit perspective, an underground discussion might be of interest and educational.
The underground paper is titled “Mining Dilution and Mineral Losses – An Underground Operator’s Perspective” by Paul Tim Whillans. You can download the paper at this link.

Here is the abstract

For the underground operator, dilution is often synonymous with over-break, which mining operations struggle to control. However, there are many additional factors impacting dilution which may surpass the importance of overbreak, and these also need to be considered when assessing a project. Among these, ore contour variability is an important component of both dilution and mineral losses which is often overlooked.  Mineral losses are often considered to be less important because it is considered that they will only have a small impact on net present value. This is not necessarily the case and in fact mineral losses may be much higher than indicated in mining studies due to aggregate factors and may have an important impact on shorter term economics.

My key takeaways

I am not going into detail on Paul’s paper, however some of my key takeaways are as follows. Download the paper to read the rationale behind these ideas.
  • Over-break is a component of dilution but may not be the major cause of it. Other aspects are in play.
  • While dilution may be calculated on a volumetric basis, the application of correct ore and waste densities is important. This applies less to gold deposits than base metal deposits, where ore and waste density differences can be greater.
  • Benchmarking dilution at your mine site with published data may not be useful. Nobody likes to report excessively high dilution for various reasons, hence the published dilution numbers may not be entirely truthful.
  • Ore loss factors are important but can be difficult to estimate. In open pit mining, ore losses are not typically given much consideration. However in underground mining they can have a great impact on the project life and economics.
  • Mining method sketches can play a key role in understanding underground dilution and ore losses, even in today’s software driven mining world.
  • Its possible that many mine operators are using cut-off grades that are too low in some situations.
  • High grading, an unacceptable practice in the past, is now viewed differently due to its positive impact on NPV. (Its seems Mark Bristow at Barrick may be putting a stop to this approach).
  • Inferred resources used in a PEA can often decrease significantly when upgraded to the measured and indicated classifications. If there is a likelihood of this happening, it should be factored into the PEA production tonnage.
  • CIM Best Practice Guidelines do not require underground ore exposure for feasibility studies. However exposing the ore faces can have a significant impact on one’s understanding of the variability of the ore contacts and the properties of minor faults.


Not everyone will necessarily agree with all the conclusions of Paul’s paper on underground dilution. However it does raise many issues for technical consideration on your project.
All of us in the industry want to avoid some of the well publicized disappointments seen on recent underground projects. Several have experienced difficulty in delivering the ore tonnes and grades that were predicted in the feasibility studies. No doubt it can be an anxious time for management when commissioning a new underground mine.
Note: previously I had shared another one of Paul’s technical papers in a blog called “Underground Feasibility Forecasts vs Actuals”. It also provides some interesting insights about underground mining projects.
If you need more information, Paul Whillans website is at http://www.whillansminestudies.com/.
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60. Mining Due Diligence Checklist

It doesn’t matter how long you have worked in the mining industry, at some point you will probably have taken part in a due diligence review. You might have been asked to help create a data room. Perhaps your company is looking at a potential acquisition. Maybe you’re a consultant with a particular expertise needed by a due diligence team. It’s likely that due diligence has impacted on many of us at some point in our careers.
The scope of a due diligence can be exceptionally wide. There are legal, marketing, and environmental aspects as well as all the technical details associated with a mining project. The amount of information provided can be overwhelming sometimes.

I’m a big fan of checklists

Checklists are great and they can be very helpful in a due diligence review. A scope checklist is a great way to make sure things don’t fall through the cracks. A checklist helps keep a team on the same page and clarifies individual roles and tasks. Checklists bring focus and minimize sidetracking down unnecessary paths.
Recognizing this, I have created a personal due diligence checklist for such times. A screen shot of it is shown below. The list is mainly tailored for an undeveloped project but it still has over 230 items that might need to be considered.

Each due diligence is unique

Not all of the items in the checklist are required for each review. Maybe you’re only doing a high level study to gauge management’s interest in a project. Maybe you’re undertaking a detailed review for an actual acquisition or financing event. It’s up to you to create your own checklist and highlight which items need to be covered off. The more items added the less risk in the end; however that requires a longer review period and greater cost.
You a create your own checklist but if you would like a copy of mine just email me at KJKLTD@rogers.com. Specify if you would prefer the Excel or PDF versions.
Please let me know if you see any items missing or if you have any comments.
Now that we have an idea of what information we need to examine in a due diligence, the next question is where to find it.
Previously I had written a blog titled “Due Diligence Data Rooms – Help!” which discussed how we can be overwhelmed by a poorly set up data room. My request is that when setting up a data room, please consider the people who will be accessing it.

Due Diligence isn’t for everyone

Due diligence exercises can be interesting and great learning experiences, even for senior people that have seen it all. However they can also be mentally taxing due to the volumes of information that one must find, review, and understand all in a short period of time.
Some people are better at due diligence than others. It helps if one has the ability to quickly develop an understanding of a project. It also helps to know what key things to look for, since many risks are common among projects.


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59. Hydrogeology At Diavik – Its Complicated

About 20 years ago I was involved in the feasibility study and initial engineering for the Diavik open pit mine in the Northwest Territories. As you can see from the current photo, groundwater inflows were going to be a potential issue.
Predictions of mine inflow quantity and quality were required as part of the project design. Also integral to the operating plan were geotechnical issues, wall freezing issues, and methods for handling the seepage water.
This mine is going to be a unique situation. The open pit is located both within Lac de Gras and partly on exposed land (i.e. islands). The exposed land is underlain by permafrost of various depth while the rock mass under the lake was unfrozen. The sub-zero climate meant that pit wall seepage would turn into mega-icicles.  Phreatic pressures could buildup behind frozen pit walls. Many different factors were going to come into play in this mining operation so comprehensive field investigations would be required.

A good thing Rio Tinto was a 60% owner and the operator

At no time did the engineering team feel that field budgets were restricted and that technical investigations were going to be limited. Unfortunately in my subsequent career working on other projects I have seen cases where lack of funds does impact the quantity (and quality) of technical data.
The Golder Associates Vancouver hydrogeologcal team was brought on board to help out. Hydrogeological field investigations consisted of packer testing, borehole flowmeter testing, borehole temperature logging, and borehole camera imaging. Most of this work was done from ice level during the winter.
A Calgary based consultant undertook permafrost prediction modelling, which I didn’t even know was a thing.
All of this information was used in developing a three-dimensional groundwater model. MODFLOW and MT3DMS were used to predict groundwater inflow volumes and water quality. The modelling results indicated that open pit inflows were expected to range up to 9,600 m3/day with TDS concentrations gradually increasing in time to maximum levels of about 440 mg/ℓ.
The groundwater modelling also showed that lake water re-circulating through the rock mass would eventually comprise more than 80% of the mine water handled.

Modelling fractured rock masses is not simple

Groundwater modelling of a fractured rock mass is different than modelling a homogeneous aquifer. Discrete structures will have a great impact on seepage rates yet they can be difficult to detect beforehand.
As an example, when Diavik excavated the original bulk sample decline under the lake, water inflows were encountered associated with open joints. However a single open joint was by far the most significant water bearing structure intercepted over the 600-metre decline length.  It resulted in temporary flooding of the decline.

Before (2000) and After (2006) Technical Papers

Interestingly at least two technical papers have been written on Diavik by the project hydrogeologists. They describe the original inflow predictions in one paper and the actual situation in the second.
The 2000 paper describes the field investigations, the 1999 modeling assumptions, and results. You can download that paper here.
The subsequent paper (2006) describes the situation after a few years of mining, describing what was accurate, what was incorrect, and why. This paper can be downloaded here.
In essence, the volume of groundwater inflow was underestimated in the original model.  The hydraulic conductivity of the majority of the rock mass was found to be similar.  However a 30 m wide broken zone, representing less than 10% of the pit wall, resulted in nearly twice as much inflow as was predicted.
The broken zone did not have a uniform permeability but consisted of sparely spaced vertical fractures. This characteristic made it difficult to detect the zone using only core logging and packer tests in individual boreholes.

Groundwater Models Should Not be Static

The original intent was the Diavik groundwater model would not be static.  It continued to evolve over the life of the mine.
Now that Diavik has entered their underground mining stage, it would be interesting to see more updates on their hydrogeologcal performance. If anyone is aware of any subsequent papers on the project, please share.

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.


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.

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.

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.


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.”


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/

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.

51. Pre-Concentration – Savior or Not?

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.


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.

48. Online Collaboration and Management Tools (Part 2)

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.

Zoom (for conferencing)

A great tool for video conferencing is zoom (https://support.zoom.us/hc/en-us).  Its similar to Skype but has added features.
It allows video conferencing, screen sharing, screen swapping.
There is a free version that provides some great functionality.




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.


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.