Environmental Mineralogy – Sustainable Minerals 2016

Environmental Mineralogy – Sustainable Minerals 2016

Petrolab’s Christopher Brough will be presenting at MEI’s Sustainable Minerals conference at the St Michael’s Hotel and Spa, Falmouth this month. He will be talking on the use of liberation analysis in humidity cell testwork. At present quantitative assessments of mineralogy, texture and mineral chemistry do not feature in the HCT assessments despite their direct control on leachate chemistry. This work explores a quantitative mineralogy approach focused on the liberation characteristics of pyrite – a critical mineral in the behaviour of mine waste. Such a quantitative mineralogical approach can supplement the geochemical approach to HCT termination, by assisting in the early termination of cells with no significant encapsulation and identifying cells which will require an extended runtime. Taken together the liberation, association and PSD data improves the overall quality of the geochemical program.  This work represents a collaboration between Petrolab Limited, SRK Consulting and Geochemic Limited. The full abstract can be viewed below.



Brough, C*., Strongman, J*., Bowell, R’., Warrender, R’., Prestia, A”., Barnes, A”’., & Fletcher, J*.

*Petrolab Limited, C Edwards Offices, Gweal Pawl, Redruth, Cornwall, TR15 3AE
‘SRK Consulting (UK) Ltd, 5th Floor, Churchill House, 17 Churchill Way, Cardiff, CF10 2HH
“SRK Consulting US Inc., Suite 300, 5250 Neil Road, Reno, NV, 89502, USA
”’Geochemic Ltd, Abergavenny, Wales


As part of the assessment of acid rock drainage and metal leaching (ARDML) potential, kinetic humidity cell tests (HCTs) are used to simulate accelerated weathering in order to predict the long-term geochemical behaviour of future mine waste material. These tests are run for a minimum of 20 weeks (ASTM, 2013) and often for in excess of 100 weeks. One of the key challenges of HCTs is the determination of cell termination. This is particularly true where there are discrepancies in prediction between static and kinetic tests, for example when corresponding static geochemical tests have predicted a significant acid-generation potential but the HCT leachate has been circum-neutral, even after 100+ weeks of testing.

One response to this uncertainty is to run HCTs for extended durations to empirically demonstrate a lack of acid generation. However, this costs substantial time and money. This paper explores a mineralogical response to the uncertainty by undertaking quantitative liberation analysis on sulfide minerals from pre-leach HCT material. The results show that pyrite liberation analysis can determine which HCTs contain a significant degree of sulfide encapsulation and therefore need to be run for prolonged periods of time. This information could also be used to increase confidence in the earlier termination of cells which contain no significant sulfide encapsulation. Altogether, quantitative liberation analysis opens up the possibility of saving time and money and improving the overall quality of a geochemical program.



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