The application of automated electron beam mapping techniques to the characterisation of low grade, fine-grained mineralisation; potential problems and recommendations

• Differences between electron beam mapping techniques are critically examined.
• High spatial resolution mapping is important for discrimination of mineral phases.
• Modern FEG instruments can shed new light on complex mineral samples.
• Electron beam microscope operating conditions determine data resolution.
• Data processing software can affect data interpretation.

Automated electron beam techniques using instruments such as the scanning electron microscope (SEM) and the electron probe micro analyser (EPMA) are commonly used by the mineral and metallurgical processing industries to characterise ore and feed materials. The correct choice of instrument and operating conditions is essential, yet often overlooked, and depends on parameters such as composition, particle size, heterogeneity and physical competency of the sample being examined, as well as the type of data sought.In this study, a thorough understanding of the analytical capabilities and the operating advantages and limitations of each instrument are discussed to evaluate and establish the application suitability. A case study is presented comparing FEG-EPMA and QEMSCAN® technologies using a sample of fine-grained (micron scale), disseminated, calcrete-hosted uranium mineralisation. The paper demonstrates how differences between results from the two instruments are principally the consequence of the operating setup and data processing, rather than instrument capability. Each instrument has a different best practice application and when used correctly (independently or together) can provide information of unparalleled quality. Both are excellent choice tools for characterisation.