Effects of sample mass on gravity recoverable gold test results in low-grade ores

Abstract

Gravity recoverable gold characterisation methodologies are the single- or three-stage tests, which generally use a standard feed sample mass. A case study of low-grade coarse gold-dominated mineralisation is presented that demonstrates the high variability of test results using different sample masses. Samples were processed using the single-stage test and subsequently entire development rounds were batched through a plant for comparison. Unsurprisingly the results indicate that the small (≤50 kg) test samples grossly understate plant gravity recoverable gold and display poor precision. Larger samples display improved precision, but still understate plant gravity recoverable gold. The small mass samples are unrepresentative as they do not contain the full gold particle size distribution. Poor representivity is enhanced by gold particle clustering. Small samples generally capture finer more abundant and disseminated gold particles, but rarely contain clustered gold. The use of standard GRG test sample masses is challenged. Test work should be based on spatially distributed representative field samples, that if required are split to representative sub-samples for testing. An early stage gold particle size characterisation programme is required to optimise sample mass and improve representivity.

Keywords

Ore characterisation Gravity recoverable gold Gold particle distribution Sample mass optimisation Sample representivity

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References

Dominy

. 2014. Predicting the unpredictable: evaluating high-nugget effect gold deposits. In: Mineral resource and ore reserve estimation – The AusIMM guide to good practice. Melbourne: Australasian Institute of Mining and Metallurgy, Monograph no. 30, pp. 659–78.

Dominy

, Murphy

and Gray

. 2011. Characterisation of gravity amenable gold ores – sample representivity and determinations methods. Proceeding of Geometallurgy Conference. Brisbane, Australia, 5–7 September 2011. Melbourne: Australasian Institute of Mining and Metallurgy, pp. 281–92.

Dominy

and Platten

. 2007. Gold particle clustering – a new consideration in sampling applications. Applied Earth Science (Transactions of the Institute for Mineralogy and Metallurgy Section B), 116, pp. 130–42.

Dominy

, Platten

and Xie

. 2010. Determining gold particle size in gravity ores for sampling and metallurgical characterisation: discussion and test protocol. Proceeding of Gravity Gold Conference. Ballarat, Victoria, Australia, 21–22 September 2010. Melbourne: Australasian Institute of Mining and Metallurgy, pp. 83–95.

Dominy

, Xie

and Platten

. 2008. Gold particle characteristics in narrow vein deposits: implications for evaluation and metallurgy. Proceeding of Narrow Vein Mining Conference. Ballarat, Victoria, Australia, 14–15 October 2008, Melbourne: Australasian Institute of Mining and Metallurgy, pp. 91–104.

Huang

and Koppalkar

. 2010. Evolution and optimization of the gravity recoverable gold test. CIM Journal, 1, pp. 221–28.

Koppalkar

, Bouajila

, Gagnon

and Noel

. 2011. Understanding the discrepancy between prediction and plant GRG recovery for improving the gold gravity performance. Minerals Engineering, 23, pp. 559–64.

Laplante

. 2000. Testing requirements and insight for gravity gold circuit design. Proceeding of Gold and Silver Forum. Vancouver, BC, Canada, 25–28 April 2000. Golden, CO: Randol International, pp. 73–83.

Laplante

and Gray

. 2005. Advances in gravity gold technology, in Advances in gold ore processing. Amsterdam: Elsevier, pp. 280–306.

10.

Laplante

, Woodcock

and Huang

. 2000. A laboratory procedure to characterise gravity recoverable gold. SME Transactions, 308, pp. 53–59.

11.

Laplante

and Spiller

. 2002. Bench-scale and pilot plant test work for gravity concentration circuit design. Mineral processing plant design, practice and control. Littleton, CO: Society for Mining, Metallurgy and Exploration, pp. 160–75.

12.

Pitard

. 1993. Pierre Gy's sampling theory and sampling practice. Boca Raton, FL: CRC Press.