Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity?

Karin Engström, Kim Harry Esbensen

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

Abstract

The conclusion from the debate over the last decade in the mining sector is that, for grade control,
reverse circulation (RC) drill sampling gives more reliable results due to less sampling problems
than blasthole samples. However, by conducting the latter with well-controlled procedures there
still exist fair possibilities to counteract the major blasthole sampling problems and achieve fit-forpurpose
representativeness, especially if based on minimal loss of fines. In the present PhD study,
extensive replicate experiments and variographic characterisations are conducted to evaluate the
performance of manual blasthole (BH) sampling and sectorial segment sampling. The experiments
were performed in LKAB’s Leveäniemi open pit mine in the north of Sweden. The experimental
area is an apatite-magnetite iron ore deposit of the Kiruna type, with the demand to exhibit a
maximum of local heterogeneity to allow the experiment the largest possible conclusion powers.
Gathering and splitting the complete BH drill cutting cones (fines cone, coarse cone) served as an
authoritative reference on which to assess the representativity of the two BH sampling methods.
Results show that manual BH drill sampling is able to produce samples with an acceptable
accuracy and precision if performed properly and with insight. Based on variographic comparison,
segment sampling shows similar precision for chemical grades as the manual sampling, while the
particle size distributions were more deviating for segment sampling than for manual sampling
at the high and low size ranges. Possible reasons for these partly surprising results are discussed.
For further investigation of the performance of BH versus RC drill sampling, a second experiment
has been planned on a parallel profile. This will result in an unprecedented opportunity for a full
variographic comparison between RC and BH sampling, aimed at designing specific, fit-for-purpose
sampling procedures as a function of ore quality, cut-off grades and important contaminant levels.
Original languageEnglish
Title of host publicationProceedings, Eighth World Conference on Sampling and Blending
Number of pages12
Place of PublicationPerth
PublisherAustralasian Institute of Mining and Metallurgy
Publication date9 May 2017
Pages85-96
Publication statusPublished - 9 May 2017
EventEighth World Conference on Sampling and Blending 2017 - Perth, Australia
Duration: 9 May 201711 May 2017
Conference number: 8
http://www.wcsb8.com/

Conference

ConferenceEighth World Conference on Sampling and Blending 2017
Number8
CountryAustralia
CityPerth
Period09/05/201711/05/2017
Internet address

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iron ore
sampling
experiment
open pit mine
ore deposit
range size
apatite
magnetite

Cite this

Engström, K., & Esbensen, K. H. (2017). Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity? In Proceedings, Eighth World Conference on Sampling and Blending (pp. 85-96). Perth: Australasian Institute of Mining and Metallurgy.
Engström, Karin ; Esbensen, Kim Harry. / Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity?. Proceedings, Eighth World Conference on Sampling and Blending. Perth : Australasian Institute of Mining and Metallurgy, 2017. pp. 85-96
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title = "Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity?",
abstract = "The conclusion from the debate over the last decade in the mining sector is that, for grade control,reverse circulation (RC) drill sampling gives more reliable results due to less sampling problemsthan blasthole samples. However, by conducting the latter with well-controlled procedures therestill exist fair possibilities to counteract the major blasthole sampling problems and achieve fit-forpurposerepresentativeness, especially if based on minimal loss of fines. In the present PhD study,extensive replicate experiments and variographic characterisations are conducted to evaluate theperformance of manual blasthole (BH) sampling and sectorial segment sampling. The experimentswere performed in LKAB’s Leve{\"a}niemi open pit mine in the north of Sweden. The experimentalarea is an apatite-magnetite iron ore deposit of the Kiruna type, with the demand to exhibit amaximum of local heterogeneity to allow the experiment the largest possible conclusion powers.Gathering and splitting the complete BH drill cutting cones (fines cone, coarse cone) served as anauthoritative reference on which to assess the representativity of the two BH sampling methods.Results show that manual BH drill sampling is able to produce samples with an acceptableaccuracy and precision if performed properly and with insight. Based on variographic comparison,segment sampling shows similar precision for chemical grades as the manual sampling, while theparticle size distributions were more deviating for segment sampling than for manual samplingat the high and low size ranges. Possible reasons for these partly surprising results are discussed.For further investigation of the performance of BH versus RC drill sampling, a second experimenthas been planned on a parallel profile. This will result in an unprecedented opportunity for a fullvariographic comparison between RC and BH sampling, aimed at designing specific, fit-for-purposesampling procedures as a function of ore quality, cut-off grades and important contaminant levels.",
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Engström, K & Esbensen, KH 2017, Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity? in Proceedings, Eighth World Conference on Sampling and Blending. Australasian Institute of Mining and Metallurgy, Perth, pp. 85-96, Eighth World Conference on Sampling and Blending 2017, Perth, Australia, 09/05/2017.

Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity? / Engström, Karin; Esbensen, Kim Harry.

Proceedings, Eighth World Conference on Sampling and Blending. Perth : Australasian Institute of Mining and Metallurgy, 2017. p. 85-96.

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

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Y1 - 2017/5/9

N2 - The conclusion from the debate over the last decade in the mining sector is that, for grade control,reverse circulation (RC) drill sampling gives more reliable results due to less sampling problemsthan blasthole samples. However, by conducting the latter with well-controlled procedures therestill exist fair possibilities to counteract the major blasthole sampling problems and achieve fit-forpurposerepresentativeness, especially if based on minimal loss of fines. In the present PhD study,extensive replicate experiments and variographic characterisations are conducted to evaluate theperformance of manual blasthole (BH) sampling and sectorial segment sampling. The experimentswere performed in LKAB’s Leveäniemi open pit mine in the north of Sweden. The experimentalarea is an apatite-magnetite iron ore deposit of the Kiruna type, with the demand to exhibit amaximum of local heterogeneity to allow the experiment the largest possible conclusion powers.Gathering and splitting the complete BH drill cutting cones (fines cone, coarse cone) served as anauthoritative reference on which to assess the representativity of the two BH sampling methods.Results show that manual BH drill sampling is able to produce samples with an acceptableaccuracy and precision if performed properly and with insight. Based on variographic comparison,segment sampling shows similar precision for chemical grades as the manual sampling, while theparticle size distributions were more deviating for segment sampling than for manual samplingat the high and low size ranges. Possible reasons for these partly surprising results are discussed.For further investigation of the performance of BH versus RC drill sampling, a second experimenthas been planned on a parallel profile. This will result in an unprecedented opportunity for a fullvariographic comparison between RC and BH sampling, aimed at designing specific, fit-for-purposesampling procedures as a function of ore quality, cut-off grades and important contaminant levels.

AB - The conclusion from the debate over the last decade in the mining sector is that, for grade control,reverse circulation (RC) drill sampling gives more reliable results due to less sampling problemsthan blasthole samples. However, by conducting the latter with well-controlled procedures therestill exist fair possibilities to counteract the major blasthole sampling problems and achieve fit-forpurposerepresentativeness, especially if based on minimal loss of fines. In the present PhD study,extensive replicate experiments and variographic characterisations are conducted to evaluate theperformance of manual blasthole (BH) sampling and sectorial segment sampling. The experimentswere performed in LKAB’s Leveäniemi open pit mine in the north of Sweden. The experimentalarea is an apatite-magnetite iron ore deposit of the Kiruna type, with the demand to exhibit amaximum of local heterogeneity to allow the experiment the largest possible conclusion powers.Gathering and splitting the complete BH drill cutting cones (fines cone, coarse cone) served as anauthoritative reference on which to assess the representativity of the two BH sampling methods.Results show that manual BH drill sampling is able to produce samples with an acceptableaccuracy and precision if performed properly and with insight. Based on variographic comparison,segment sampling shows similar precision for chemical grades as the manual sampling, while theparticle size distributions were more deviating for segment sampling than for manual samplingat the high and low size ranges. Possible reasons for these partly surprising results are discussed.For further investigation of the performance of BH versus RC drill sampling, a second experimenthas been planned on a parallel profile. This will result in an unprecedented opportunity for a fullvariographic comparison between RC and BH sampling, aimed at designing specific, fit-for-purposesampling procedures as a function of ore quality, cut-off grades and important contaminant levels.

M3 - Article in proceeding

SP - 85

EP - 96

BT - Proceedings, Eighth World Conference on Sampling and Blending

PB - Australasian Institute of Mining and Metallurgy

CY - Perth

ER -

Engström K, Esbensen KH. Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity? In Proceedings, Eighth World Conference on Sampling and Blending. Perth: Australasian Institute of Mining and Metallurgy. 2017. p. 85-96