1/9Thread: WHAT TO LOOK FOR ON YOUR NEXT SITE VISIT to any open pit mine: Floor conditions & big rocks. If the floors r not smooth, level & clean -like tabletop- then the trucks will be less productive &mining cost higher than average. The Big rocks are the 1st sign of of trouble
2/9 Looking up from below at that lower bench in the prev. pic you can see a lot big rocks have been pushed over the edge of the bench. While this immediately postpones the problem, the No. of big rocks on each bench increases as the pit deepens, ↘️ decreasing productivity.
3/9 Here, on another bench you can see how big rocks affecting productivity. The guys are drilling off a blast pattern on the left, and truck access hampered on loading bench below, making loading & hauling complicated and very expensive.
4/9 Also, there may be protrusions of solid rock not yet seen sticking up from the bench below that also have to be treated to get the floor level. In talking with the team, they pointed out the big rocks appearing in the blasts (below), blaming faulting & rock hardness.
5/9 Rock Breaking is sometimes done with a mechanical "pecker" or rock breaker (eg. from elsewhere on the right) but very slow and painful b/c the equipment breaks down a lot. Its a little cheaper and faster to do 2ndary blasting instead, but that comes with its own problems too.
6/9 If the rock is smaller than about desk-size the simple solution is to place bombs on top of each rock. If the rocks are bigger, it is better to drill (again) & blast the charged up holes (eg. from elsewhere below). Either way its expensive, time consuming & hazardous work.
7/9 A rule of thumb is that 2ndary blasting is 2-3 times more expensive than primary blasting, but the knock-on increase in load & haul costs is often forgotten. So, it is ALWAYS better to make adjustments to your primary drill & blast design & process to improve fragmentation.
8/9 The easiest way to improve fragmentation (reduce size & No. of rocks in a blast) is to increase the density of explosives (powder factor) per t of rock blasted, by reducing the burden and spacing. This increases D&B cost/t but also 2ndary blasting costs & milling costs.
9/9 In the case study shown, it took 8 months & 20 extra guys to blast 400kt! of big rocks, along with a reduced burden & spacing on the drill patterns, a reduction in hole diameter to resolve the problem. After this the total mining cost reduced 22% overall⬅️Higher productivity

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More from @NeilRingdahl

Aug 26, 2021
$Fil Filo Review/Thread No.1
1/ 1 needs to spend time on the data, reading background reports, looking at plans etc. & I have been doing this while waiting for a couple of answers from the Co. on its dataset available on the website. Nothing major, just a couple of questions on Image
2/the differences between the RC & DDH drill survey data. If I have wonkey survey data, or bring the data in wrong, I'll get wrong sample positions, which would lead to wrong models &designs➡️different economic outcomes &then we know it could all end in tears➡️ not good.😁
3/ So while we wait its a good time to review the PFS report by Ausenco. Very nicely presented, clear & professional it answered some of my initial doubts about water & land/sovereign risk. Need to spend more time on the Chilean vs Argentinian laws & its impact on a mine ImageImageImage
Read 12 tweets
May 4, 2021
1/8 Dimension Stone (DS): Now if there ever was a cut-throat business, it would be this one. Worse than the diamond industry in terms of competitiveness, it seems the Taiwanese & the Italians have pretty much cornered the market. This particular granite mine is in Zimbabwe🇿🇼
2/8 Dimension stone is a really messy mining business with quite a serious environmental footprint. Hard to rehab the holes and tonnes of oversize rubble. Blame the banks & other rich Co's that want beautiful skyscrapers & floors, for example the Scotiabank building in Toronto.
3/8 Only 10-25% of what is mined goes out as sellable product. This is because its only possible to sell big, clean blocks with no faults or joints; natural weaknesses which cause a block to split when it is cut by a diamond saw. Breaks easily. Blocks are huge & generally
Read 9 tweets
Jun 26, 2020
1/23 #Economics of #OpenPit #Mining & its impact on a Mining Co's success. This brilliant pic of Letseng diamond mine in Lesotho shows the results of sensible & good strategic & tactical mine #planning. Take a careful look and then compare this pic to the next one of
2/23 Guyana Goldfields, which is an example of what NOT to do. At first glance, the two pits don't look too dissimilar, right? But what from these pictures is it that lead to the disaster & ultimate collapse sale of $GUY, while GEM Diamonds is still doing great? Can you tell?
3/23 The answers is in the phasing of the pit & ramp access. GUY's next pushback (yellow) is constantly cutting off access (red) to the cut below from blasting -The only cut which supplies the gold. They have to mine the yellow cut/pushback to expose ore later on but it looks
Read 24 tweets
Jun 2, 2020
1/7 @BigQuestionsNow A Q about this chart you or someone can help me with: We have high Ag/Au at the top of our mine moving to Zn/Pb/Ag w/ decreasing Ag, no Au at depth. Below that we expect & start 2 c more Cu. But in this graphic there is Cu-Au. Does this model work for us?
2/7 The Zn-Pb-Ag mineralized zones that comprise the El Mochito deposit are classified as distal zinc skarns as defined by Meinert (1992). You'll see the wildcat hole we are planning in the graphic below, probing for a heat source, which has, until now been elusive. The highest
3/7 Cu grades (of 0.7%) in the mine are patchy, never considered economic but can be found close to the collar of this new hole in that thicker manto area. We have high Ag grades in the vertical chimney orebodies, and mostly base metals at the bottom. Geology background below.
Read 7 tweets
May 23, 2020
1/10 Here's the thing about many MINING TECHNICAL CONSULTANTS: Its not about the software, its about the assumptions used in the JORC or NI 43-101 docs. If you know how, you can make a bad project look quite good and a good project look bad. I call it
2/10 "Sum of the assumptions effect," with either a conservative or optimistic slant. There are literally hundreds of assumptions which can be manipulated to get to the desired objective. For example lets just look at how a resource & reserve changes with relatively small diffs
3/10 The impact is exacerbated when taking these assumptions into an mining, economic schedule and that's assuming we don't vary the financial assumptions much. It's an art & if you're good at it few will notice what is is being done.
Read 14 tweets
Mar 22, 2020
1/16 So where was I going with #mining block models in my previous thread? I can now show you how we use them to optimise for open pit mining and approximate a good UG mine plan as well. To begin, the decision to go open pit or UG very much depends on the shape & size of the ore
2/16 body, and the decision is usually intuitive. Sometimes a combination of OP & UG methods makes more sense. Consider the following theoretical block model representing a rich, vertical ore body. Assume this is a 2D environment, not a 3D one, with coloured units of value.
3/16 Now with our avatar safely removed w/o any major social justice fallout, we can get on with the open pit mining. 😉 Let's assume that the cost of mining is 1 unit, processing cost 0, what would the value be mining the 1st level by Open Pit methods?
Read 17 tweets

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