What is the different between Lab XRF and Hanheld XRF, is it accurate and useable to analyze sedimentary rocks?
In the lab you can analyze under vacuum even very light elements. You have homogenized powdered samples which you prepare with a well-defined matrix compound and a well-defined surface of the samples. You have standardized measuring conditions. These are analytical conditions which you can never expect in the field. For mining and exploration according my experience this handheld XRF device is a good tool for capturing chemical digital data in the field or in the core shed, because you expect heavy metals and in mines and cores metals at ore grade.
H.G.Dill
In the lab you can analyze under vacuum even very light elements. You have homogenized powdered samples which you prepare with a well-defined matrix compound and a well-defined surface of the samples. You have standardized measuring conditions. These are analytical conditions which you can never expect in the field. For mining and exploration according my experience this handheld XRF device is a good tool for capturing chemical digital data in the field or in the core shed, because you expect heavy metals and in mines and cores metals at ore grade.
H.G.Dill
This device is for getting an approximate chemical composition of the sample/s. But the data cannot be used for research as the point of analyse will vary depending upon mineral or matrix and the data will be that of the mineral grain or matrix.
We should have high precision data of the samples concern to have the correct interpretation of the study. This can be achieved only under the homogenized condition of the samples/ rocks. This device can be used for getting the data quickly in a naturally uniform composition like the case of ores.
We have very good 10 years long opinion using of handheld XRF Niton 3+ Gold within Miocene sedimentary series (mostly clays) of the Most Basin, Czech Republic. We use it during research and usual production purposes on our lignite mines. It is especially useful for expectation of long borehole profiles searching changes og geochemical proxies. We alsou can correlate profiles on outcrops of our opencast mines with prospection borehole profiles.
We use it often for detail sampling just on the core in field, sampling on core intervals 0.1m to 0.5m. For measuring we only prepare a little flat area on the core by knife or other tool and than 30 seconds goes sampling. 1 minute aproximately one sample... Very effective. During one shift You can sample hundred metres of core, going home with ready data. Normaly we made 200 - 500 samples per borehole by this way. Obtained log is very similar to geophysical log by its detail and enables corellate very thin sedimentary units between boreholes. Our handheld were calibrated for our clays by seller of this equipment. We also use classic sampling with later analyzing by table XRF. It is more accurate, it is clear, but You need several times more time and more people working in the lab preparing samples for laboratory measurements. To increase acurracy of XRF handheld You can recalibrate your results (simply recalculating results by find regressions) on the same samples measured by different methods.
Karel
I have used a handheld XRF for soil geochemical analysis. The first thing to do is to have proper training, especially for safety. The X-rays are dangerous. Hand-held XRF machines are a very useful reconnaissance tool, but do not rely on them for accurate results. A major consideration is the grainsize of the target rock or soil. The machine only sees a small area of sample and a few millimetres depth. Another consideration is the shape of the surface being analysed - is it perfectly flat or round like drill core, or irregular with air spaces? Next is detection limit and that varies for each element. As far as I know the portable XRF will not detect low amounts of gold, and the one I used seemed to exaggerate the amount of silver in the soil. Next there are interference effects, such as iron causing false readings for cobalt. So good training is needed.
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