Interview with a Geologist; Do Sample Prep Tools Add Value to Portable XRF Analysis in Mining Applications?

Portable X-ray Fluorescence (XRF) instruments offer many operational and cost benefits to the mining industry. They provide a cost-effective alternative to expensive, permanent, on-site labs or costly and untimely sample dispatch to off-site laboratories. However, in many cases, the key to achieving better correlation with laboratory results using portable XRF is proper sample preparation. We interviewed a leading geologist about the pros and cons of portable XRF and sample preparation in mining elemental analysis.

Q: Tell us about your experience with portable XRF technology for this application. A: I have used portable XRF in various projects, from precious metals to base metals. The detection limit for many elements, particularly base metals, is good enough, and reliable data can be created in the field which helps the geologists to make decision onsite, particularly if you are drilling. However, the user should understand the limitations of this technique before using it. For example, if you are looking for an element in concentrations close to the detection limit of that element, most probably you will not get the accuracy that you need. Q: Can this limitation be overcome? A: Sample preparation is the key if you are looking for higher accuracy data. This is especially true for strongly altered and mineralized samples. Q: What does sample preparation accomplish? A: Sample preparation creates a homogeneous sample, which is extremely important because sample composition and sampling techniques can greatly impact results. Samples that come out of a mill or similar device are fine-grained and contain more consistent particle sizes than any other type of sample. A powdered sample is more representative of the sampling media and will produce consistent and repeatable assay data. Non-homogenous samples contain different concentrations of elements at different points across the sample. The best solution for inhomogeneous samples is to fully prepare them, which then homogenizes the sample in the process. Q: When would you choose to forgo sample prep? A: I have seen users who prefer to get data fast on unprepared samples, even in drill cores for trend analysis. So, the bottom line is time: higher accuracy on prepared samples, which takes a few minutes to prepare each sample, or lower accuracy on unprepared samples. A recent study evaluated how portable XRF analysis may be enhanced with sample preparation. To see the results, including the correlation curves, repeatability data, methodology, and comments, read Use of Sample Preparation Tools in Mining and Mineral Exploration Projects.