Characterisation of silver minerals in lead-zinc flotation tailings and their resposne to cyanidation

Rohde, M., Guresin, N. and Johnson, N. W. (2014). Characterisation of silver minerals in lead-zinc flotation tailings and their resposne to cyanidation. In: 12th AusImm Mill Operators' Conference 2014: Proceedings. 12th AusIMM Mill Operators' Conference 2014, Townsville, Australia, (163-172). 1-3 September 2014.

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Name Description MIMEType Size Downloads
Author Rohde, M.
Guresin, N.
Johnson, N. W.
Title of paper Characterisation of silver minerals in lead-zinc flotation tailings and their resposne to cyanidation
Conference name 12th AusIMM Mill Operators' Conference 2014
Conference location Townsville, Australia
Conference dates 1-3 September 2014
Convener David Hunter
Proceedings title 12th AusImm Mill Operators' Conference 2014: Proceedings
Series The Australasian Institute of Mining and Metallurgy Publication Series No 9/2014
Place of Publication Carlton, VIC, Australia
Publisher AusIMM: Australasian Institute of Mining and Metallurgy
Publication Year 2014
Year available 2014
Sub-type Fully published paper
Open Access Status
ISBN 9781925100143
Start page 163
End page 172
Total pages 10
Collection year 2015
Language eng
Formatted Abstract/Summary
A lead-zinc flotation tailings sample containing silver from BHP Billiton's Cannington Mine has been characterised to understand occurrences of silver in the tailings by conventional elemental, X-ray diffraction (XRD) and size analyses followed by mineralogical analysis with a scanning electron microscope (SEM) equipped with mineral liberation analysis (MLA) software and the use of an adapted diagnostic leach process originally developed for gold containing materials.

The tailings sample contained 67 g/t Ag, 1.8 per cent Pb and 0.52 per cent Zn. The XRD analysis showed that the sample consisted of 74 per cent silicates, nine per cent sulfides, 11 per cent magnetite and small amounts of other minerals such as fluorite, fluorapatite and rutile. The p80 and p50 of the sample were determined to be 106 11m and 38 11m, respectively. The silver distribution was high in the small size fraction with 52.1 per cent of the silver being in the -8 11m fraction. The silver minerals freibergite, acanthite, jamesonite, pyrargyrite and native silver were observed in the mineralogical analysis of the sample by SEM/MLA. The associations of the minerals were intricate and the occurrences of silver were complex. There were finely disseminated silver minerals and also coarser grains of silver minerals in composites with the host minerals. It was estimated that almost 50 per cent of the silver was contained in pyrargyrite, around 14 per cent as native silver and contained in acanthite, 12.5 per cent in galena and around ten per cent in freibergite and jamesonite.

These composite particles and the type of the silver minerals present were expected to limit leaching efficiencies of the silver in hydrometallurgical processing. The diagnostic leach tests showed that around 50 per cent of the silver could be recovered by direct cyanidation and higher extractions could be achieved by more aggressive acidic systems.

Cyanidation tests were conducted to confirm the findings of the diagnostic leach studies. The investigated cyanidation parameters were time (up to 48 hours), solid to liquid ratio (1:1 and 1:2), cyanide concentration (0.025 M, 0.5 M and 0.1 M) and particle size (p80 of 106 µm, 63 µm and 7.5 µm ).  The effects of oxygen and lead nitrate were also studied. The tests were conducted at atmospheric temperatures. The maximum silver recovery obtained was about 50 per cent for all the parameter ranges trialled except particle size. The decrease in particle size from 106 µm to 7.5 µm by fine grinding resulted in an increase in silver recoveries from 50 per cent up to approximately 82 per cent indicating that the liberation of the silver grains/ minerals is one of the factors affecting the cyanidation recovery of silver in addition to the presence of refractory silver minerals not amenable to cyanidation. 

Low head grades of silver in the tailings and relatively low cyanidation recoveries of silver (without fine grinding) necessitate a thorough cost analysis for the cyanidation of the Cannington lead and zinc tailings to assess if cyanidation would be a suitable process option for the extraction of silver. It is clear that one of the most important factors in determining the cost feasibility will be the price of silver in the world metal market.
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Q-Index Status Confirmed Code
Institutional Status UQ

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Created: Tue, 09 Sep 2014, 10:49:49 EST by Karen Holtham on behalf of Julius Kruttschnitt Mineral Research Centre