🧵Mining 101: The #Economics of #OpenPit vs. #Underground #Mining, following on from the thread below.👇❗️
Why are some mines underground (UG), others Open Pit (OP) & others a hybrid of the two?
We will mainly discuss mine economics here, but there are others reasons too... 1/13 OP mines are obviously cheaper (per tonne) to operate than most UG mines. That said they often require more Capex. Also an OP mine is an eyesore & can leave a lasting/permanent mark on the landscape. They are becoming globally more difficult to permit. 2/13

Shaft Sinking 101:
A really excellent showpiece on shaft sinking activities on one of Oyu Tolgoi's new 9m diameter, circular shafts. 👇😃
Shaft sinking is a very exciting & hazardous mining activity. It also costs a lot of money.
I will explain some of the seen activities in this🧵 1stly, this shaft is in "Main sink" phase, which takes place after the pre-sink is completed to a depth of ~80m. You need this space to fit in the sinking "galloway" stage, which I will explain later.
The opening shot is that of the shaft bottom from a kibble rising up from shaft bottom into this galloway. The shaft is being prepared for drilling the next round to blast (in the floor).
The Drill jumbo (center) is already lowered & the guys are completing drilling sidewall support holes with handheld jack legs(far left, top center, lower left & far right). The two clamshell loaders are also still fully extended to the # bottom for loose rock to be manually cleared into their buckets from the sidewalls. You can see the split sets &end plates used in the sidewall support lying at bottom of pic. 2/17

Good tactical & strategic planning along with execution is more important than grade. A 🧵

Our case study today is Pure Gold $PGM
& how it turned into Pure ..💩

1st, some theory you'll know if you have been following me 4 a while:
/1 These concepts are important because the decision was to use large trackless machines in the mining of the new access ramp & therefore say to say all ore development will be of a similar size as well. We should therefore expect dilution issues in narrower orebodies of Marsden /2

#Mining with Electric machines: A modern miracle to save the environment or a pipe dream? 🧵
I'll discuss both open pit & underground apps.
For 60yrs, engineers have been innovating electric mining machines b/c they're cheaper. An electric dragline moves 60t each swing.😳1/ These monsters are so huge, a ship's diesel engines don't cut it. Way before I was even born, the clever guys worked out its cheaper -on a per-tonne basis- to use electric motors connected to the grid. They work well and are excellent in soft-rock stripping operations. 2/

The DANGERS of spreadsheet mining. A🧵

Some of you may have been following the $AUN debacle, a good e.g. when the Lassonde curve goes south. 😬

I will discuss a few important technical flaws in the Aurcana investment thesis. /1 A couple of things in the 2022 Feasibility study Mineral Reserve Estimate immediately jump out.
1- The reserve is small
2- The min. mining width is crazy
3- The dilution No.'s seem too precise

One thing mining is not is precise. It can be accurate, but that's a different thing/2

1/ Lets review this Q:
@Darken_Man got it right, well done.
Look at the pit floor: Very uneven, by far the biggest negative impact on this operation. Why? Slower reversing in, slower truck tramming, more difficult loading & damage to tyres. "How so?", you may ask.
Thread:

https://twitter.com/NeilRingdahl/status/1562618014851563520

2/ Have you ever driven a car on a really bad road? Its slow and hurts the car. With trucks its way, way worse b/c trucks are the most expensive part of the open pit mining biz. & they're also the production conveyor that moves your product in diluted form to the plant.

1) Thread: From Drilling to Open Pit Optimization For Dummies.
Imagine you have project and hire a truly great geologist who has drilled some fantastic looking sections based on a small surface anomaly he found from a surface geochem sampling program. 2) Your geologist (lets call him George) tells you its a pipe-like copper skarn, vertical in nature about 50m wide and open at depth that he interprets (a key word here) in section in this pic below. (We will keep things simple by staying in only two dimensions X & Y).

1/11 $REG REVIEW Thread: - I'm a hopeful shareholder, underwater🙄for 3yrs now. Bought it at 1.65 - yeah crazy I know. Here's a review & why I'm still in. The pic below says it in 1000 words. 2/11 Probably the most important point is the property is and in particular the resource is part and the same of an adjacent operating mine, Tantahuatay, which is 40.1% owned by Buenaventura (the operators), 44.2% by Southern Copper & 15.7% by Regal Ware Inc. out of the USA.

1/8 Oh my Gatos THREAD: $GATO got hit so hard today! -69% 😵A potential 30-50% reduction in MRMR tends to do that. Kudo's to them for disclosing all the bad. This is legally required but many don't. In figuring out HOW/WHY while we wait for the formal explanation in H2, I noticed

https://twitter.com/Vtradez/status/1486485642179604483

2/8 a cross section in the tech report showing the block model vs. drill composites, that the grades may bottom loaded in the veins; or veins were modeled wider than they actually are or, the block model extended beyond where it should have.

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.

$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 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.😁

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.

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?

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?

https://twitter.com/BigQuestionsNow/status/1267730248298164224

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

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

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.

1/9 BLOCK MODELLING: Imagine you have a gold ore body that looks like this in section after your geologist has done his interpretation. To keep things simple, let's assume you are very promotional QP who is comfortable with just two drill holes to build your resource 😏 2/9 In the drawing above the line representing the ore body (blue) is the geological INTERPRETATION based on known info. The block model is essentially an integration of slices (or blocks) of that interpretation so we can model all the variable properties that make up that shape.

1/6 This is a really nice pic showing what "double-sided loading" means. Single-sided loading implies there is only room to reverse one truck in next to the shovel. What it implies is that the second truck will be filled faster than it otherwise would have been, not having to

https://twitter.com/miningnews/status/1226732289293312007

2/6 wait off to one side for the 1st truck to be loaded and pull away, then reverse into position. You might not think the 30 seconds or so in lost time is that much until you sit down and do the calculation (see below). Of course, this assumes each truck is always going to save

1/18 MINING COST ASSUMPTIONS r subjective & r based on many variables, e.g:
Currency, country, mining Co, hrs worked, % local materials, tax, import duties, power type & cost, productivity levels, mining method, depth, geotech, rock hardness, size of resource etc. etc. So how... 2/18 can one make any reasonable cost assumption for a particular mine? The answer is simple: BENCHMARKING and if you can, ZERO-BASED COSTING which is hard work. Experience is a critical element in this. By experience I mean 5-10yrs 3D computer mine planning just does not cut it.

1/14 DUMP TRUCKS: The conveyor belt in open pit production. The most important & normally the biggest cost element in open pit mining - hauling ore & waste. Here is a pic of one of the most widely used & successful OP trucks ever built. The CAT 793. Over 2600HP,
this beast... 2/14 has a capacity of 220t rock each load. Fuel tanks carry 1,150gal/4,350L of diesel which is burned up in 16-20hrs. A mine truck is a highly engineered piece of equipment. Look at the catalogue: bit.ly/2mkjl3K
The 6 tyres are typically pressurized to around

1/15 THREAD: Gold metal accounting, East Katanga -DRC- style

Hats off to these guys.

UG Mining using hand implements. Head grade 3-5 g/t Mining recovery 40%. -> 7.5t moved for 1 tonne of ore. Mining dilution 0% -> Hand pick the ore. 2/15
Look at this workmanship! This particular hole was 36m deep & consisted of about 30 x 1.2m high steps. At the bottom, they rat hole in all directions along the structure. Scary stuff geotechnically, but they're way better than most trained geologists at finding pay shoots.