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Gold clusters in Arsenopyrite (APT)

Every year, tons of ore are crushed and processed to extract the small quantities of gold contained within. Techniques such as X-ray fluorescence microscopy can localize the gold on the micron scale, but 3D atom probe analysis provides the highest resolution of the gold distribution at the atomic scale which can help to optimize the extraction processing for a more efficient mining operation.

The LEAP Atom Probe has the ability to find tiny ‘invisible’ gold in refractory minerals such as arsenopyrite that can contain traces of locked gold. It can provide information of the position and type of individual atoms by the rate the gold atoms contained in the mineral evaporate, which is then 3D­-imaged on a computer.

Compared to other microanalytical methods used to identify gold-bearing regions within a mineral, such as AFM, Atom Probe Tomography is uniquely capable of revealing large differences in the atomic-scale distribution of the gold atoms. In some regions, the gold is clustered in domains measuring a few nanometers in size. In other regions, the gold is distributed homogenously, but from grain to grain the gold concentration could vary by an order of magnitude.

Data from Fougerouse, D., S. M. Reddy, D. W. Saxey, W. D. A. Rickard, A. van Riessen, and S. Micklethwaite (2016), Nanoscale gold clusters in arsenopyrite controlled by growth rate not concentration: Evidence from atom probe microscopy, American Mineralogist, 101(8), 1916, doi:10.2138/am-2016-5781CCBYNCND.