Hiding high grade ore in a raise badly needed for ventilation and insisting that the raise was filled with waste. Emptying the raise on the weekend and then filling it up again.

Exaggeration of both grade (by 100%) and then tonnage output by (100%) at an operation lacking the means to reconcile production from different mines.

Driving a spiral ramp down from surface to a place that had access via another ramp system as well as an adit from surface.

Installing a mill before accessing the mine and then finding out the mine would not make money ? That has happened numerous times.

Lots more examples I wish I could share.

Although some say the client is always right, I consider that the cost of going against our common sense and best practices is much higher we think. Moreover, the choices we make in this regard will determine the work environments in which we prosper and the work environments in which we starve for air. Considering that our work becomes a lifestyle and that the majority of us spend more time at work than we do with our families, who do you want surrounding you during your hours at work? Paul Tim

1. How does your software handle self-intersecting faces inside the solid?
2. When you hit water with the laser at a certain angle, the laser sometimes bounces off like a mirror and you get the correct angles from the laser but an erroneous distance.
3. When the laser hits a bolt or screen sticking out from the back or wall into the stope void it will register as a point on the CMS.
4. What happens when you have two CMSs taken from different locations and one is smaller than the other at one end of the stope and larger at the other end when viewed in section. Which one do you choose, ie How do you handle the shadows?
5. What happens when a CMS hits backfill. Sometimes no reading.
6. I can´t think of how an algorithm could be designed to compensate for all of these features. What I can understand is that an algorithm could be designed for:

1. Selecting the farthest points away from the location of the laser and eliminating the others but this may not be what you need;
2. Eliminating extraneous points.
3. I think in today´s world drill sections and therefore blast hole drilling should be in 3D.

Conclusion : I would take the raw CMS, overlay it on the drill sections and manually draw a polylines. Then create a new solid and compare it to the design solid to report on dilution and mining recovery, which I call percent mined to avoid confusion with metallurgical recoveries.

It takes an interest and effort to do the work and in most mines there is not an interest to do this basic work; may because it is too often assigned to surveyors who have other priorities. The people doing the blast layouts, those with a vested interest in seeing the blast come out well, should be the ones taking these readings in my opinion.

• For upholes you have to bend back (see attached photo) some people don´t like to do that.
• For downholes you have to dirty yourself by pulling out the cones one by one, then you have to take off your gloves take the reading and put the cones back. Can take a number of hours to check a stope.
• This opens up another opportunity, that of checking at what depth downholes start to deviate. With a flashlight in the hole, it makes it much easier to take an accurate reading.

Recommend doing it with two people, because one can illuminate the dial, take notes, figure out which hole you´re on and leaf through print outs of the drill sections. The other person shines the light up the hole and shouts out the reading. It is possible to illuminate the dial and shine your light up the hole but it takes a bit of skill.

The timing of when you take these readings is important. No point in waiting until after the drill has moved out; so this is somethings that should be done as the drill is working. The mere fact that someone is seen to be checking the rings will, in itself result in improved drilling.

• A desktop professional estimates the dilution of a narrow vein at 15% and the block model gives a background grade of 0.5g/t in a mine that has a cut off grade of 5g/t.
• A second professional looks in detail at the amount of dilution and finds that 60% is a reasonable expectation for that mine. (Not an uncommon finding by the way) Even if the second professional uses an average value for the background grade, in fact, even if 0g/t is used, that estimate will be closer to the truth.

Remember also that dilution comes from different sources, each with its own impact on metallurgical recoveries. For example :

• How does the cement or reagents in the backfill affect the recoveries at the mill? How do we factor that into dilution? (remember it has a different density)
• What about ore contact variability (sinuosity)? What if we didn’t mine the ore because the contact wiggled out of the mining zone and all we got was mostly waste! What dilution factor would you use for that?
• What about an LHD operator who dumps ore in a remuck bay on top of some waste
• What about the truck driver who gets confused about where he is taking his load waste dump or ore dump? This happens and frequently…
• What about loss of fines in the muck?

I think you might see that the exact value of the background grade can quickly become less important than other factors.

– Paul Tim Whillans