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SPECIALIST EQUIPMENT


REMOVING GANGUE MINERALS


Simon Isherwood presents the third part in a series of articles on meaningful process mineralogy, this time focusing on eliminating gangue in concentrate


E


arlier articles have illustrated how automated scanning electron microscopes can be used to help with the choice of reagents to solve metallurgical problems in tailings.


Here, we will discuss how the process can be used to reduce gangue minerals in concentrate streams. A-SEM data is now regularly used to identify the gangue minerals in fl otation concentrates and can be used to focus eff orts on their removal. In the Betachem/Nasaco process mineralogy laboratory in Johannesburg, the team develops chemical solutions to the standard problems of poor concentrate grades. Client samples are scanned using one of the lab’s three A-SEM units (MLA from FEI). Gangue minerals are identifi ed and particle size measured. Treatment methods are then suggested with reagent testing as appropriate.


T e following text explores the fi ve basic


reasons why gangue minerals report to concentrate.


Naturally fl oating gangue mineral In the platinum fl otation concentrate shown in Fig.1. the PGMs are present as discrete PGMs and also locked with the three sulphide minerals. Talc and pyroxene are present in the fi nal concentrate as naturally fl oating gangue. 69% of the talc and pyroxene are present as fully liberated 10-212µm particles. T e talc and pyroxene were eliminated with the use of a specifi c talc depressant.


Gangue locked in valuable mineral In Fig 2. this polymetallic fl otation plant was producing poor zinc concentrate grades. 57% of the dolomite gangue is locked in the sphalerite grains. T e only way to improve this


ABOVE: The Betachem/Nasaco process mineralogy laboratory in Johannesburg, South Africa


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