Blasthole Cone Sampling Experiments for Iron Ore Flitch Mining

by

Gareth McArthur, Craig Jones and Mark Murphy

Sampling 2010

Thanks to :

Rio TintoGareth McArthur and Craig JonesMine teams at Mesa A and Mesa K

Acknowledgements

Blasthole?Blasthole cone?Flitch mining?

Definitions

What is a blasthole?

What is a blasthole cone?

http://www.youtube.com/watch?v=X3-tbT-_k2Y

What is flitch mining ?

BackgroundGeology

Mesa A

Mesa A/Warramboo

www.epa.wa.gov.au/docs/2566_Bull1264_170907.pdf

Mesa A -simplified geology

Mesa A – geology in mine portal

Mesa A – geology - annotated

Assumptions for flitch miningMethods of sampling

Blasthole cone sampling

Blasthole cone: the 2 : 2: 1 assumption

2 (40%)

2 (40%)

2 (20%)

Blasthole cone: Sampling method

1. Identify two high points2. Cut to slots, A and B3. Sample increments from

faces using the 2:2:1 rule4. Reject the sub drill

increment5. Combine the respective

flitch increments from the A and B slots into the final samples

ProcessHole depth versus sampling face cone heightVariation in cones heights/shapesPainting the cones to mark sampling intervals

Sampling experiments

Sampling experiments1. Test the blasthole rig at Mesa J destined for

Mesa A2. Track the actual depths drilled sampling

interfaces3. Paint the cone at the sampling interfaces4. Collect samples using the 2:2:1 rule on cone

face5. Measure actual sampling interfaces heights

using paint6. Collect second samples using reference paint

marks7. Compare the results

Blasthole depth versus cone height

Cone heights/shapes varies

Painting the cones – white or pink?

Sampling faces – paint lines

Depths to sampling boundariesSampling intervals in cone facesComparison of blind (2:2:1) to painted

sampling intervals

Sampling experiments - results

Depths to sampling boundaries 126 holes

Plot shows the drill rod measurements of end of flitch – driller estimation error

Layer proportion in blasthole cone 126 holes

2:2:1 samples/paint delimited upper flitch

Fe LOI SiO2 Al2O3 P

Mn

TiO2 CaO MgO S

2:2:1 samples/paint delimited, lower flitch

Fe LOI SiO2 Al2O3 P

Mn TiO2 CaO MgO S

Conclusions

Ratio of material report to blast cone is highly variable

Sub-drill is often over represented in the cone by a small fraction

Flitch samples in the cone are on average equal proportions but with high variation from hole to hole

Despite noise and difference between paint-marked actual and 2:2:1 estimated sample intervals grades are similar (albeit noisy) when compared.

Paint markings of boundaries should improve precision.

Conclusions

More detail in AusIMM Publication SAMPLING CONFERENCE / PERTH, WA, 11 - 12 MAY 2010, p 131 to136.