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Principal component Analysis Applied to ToF-SIMS Identification of PGE Minerals and Gangue Minerals

Anglo Platinum Management Services

Project Duration: 2005-2007

Funding: Anglo Platinum Research

Chief Investigators: Roger Smart, Brian Hart**, Mark Biesinger**, James Francis**
 

Description:

Identification of the surface chemical factors affecting flotation separation of a value sulfide phase requires measurement of the hydrophobic and hydrophilic species that are statistically different between particles of that mineral in the concentrate and tail streams.  Statistical methods, based on the monolayer-sensitive time of flight secondary ion mass spectrometry (ToF-SIMS) technique, have been developed with this ultimate aim (Smart et al., 2003).  These methods involve the measurement of hydrophobic species (particularly collector ions) as well as hydrophobic metal ions, precipitates and added depressant species.  Reliable identification of specific mineral particles is central to this statistical analysis.

Principal component analysis (PCA) identifies combinations of factors strongly correlated (positively or negatively) from sets of spectral data displayed as in images.  PCA selects these correlations from the ToF-SIMS mass spectra recorded at each of 256x256 pixels in a selected area of particles.  In the image mode, PCA has proved to be a much better method of differentiating mineral phases and selecting particles (regions of interest, RIOs) of specific mineral phases with clearer definition of particle boundaries due to multi-variable recognition.

Objectives

• To establish whether PCA of ToF-SIMS data from plant samples can recognize PGE minerals, base metal sulfides and gangue minerals in concentrates and tails.
• To explore the application of PGR principal components to defining ROIs for these minerals.
• To directly compare principal components selective for PGE, sulfide and gangue minerals between concentrates and tails without ROI selection.
• To transfer this methodology to Anglo Research Centre in training workshops on the use of the PCA methods and the interpretation of the principal components.

Smart R.St.C., Jasieniak M., Piantadosi C. and Skinner W.M. (2003), "Diagnostic Surface Analysis in Sulfide Flotation", Proceedings "Flotation and Flocculation: From Fundamentals to Applications", (Eds. J. Ralston, J.D. Miller and J. Rubio)  ISBN 0-9581414-0-1, 28 July - 2 August, 2002, Hawaii. Publ. Ian Wark Research Institute, University of South Australia, 341 - 248.



** Surface Science Western, University of Western Ontario, Canada
 

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