<p>R. Gerhard Merker - mineral processing engineer (MMP) Use of virtual fractions for MLA of Y- bearing REE ores</p><p>Authors: </p><p>R. Gerhard Merker (MMP Elpenrod), Prof. Dr. Bernhard Schulz (TU-BAF Freiberg), Thomas Leißner (TU-BAF Freiberg), </p><p>Abstract:</p><p>Rare earth ores enriched in critical rare earth elements (CREE) are currently of particular interest. The CREE are Nd, Eu, Tb, Dy, including Y. </p><p>In conjunction with beneficiation tests on Y-mineral bearing flotation tailings with complicated mineralogy, the authors applied the Mineral Liberation Analyses (MLA) to processing characteristics in terms of modal mineralogy, mineral recovery, locking/liberation and particle size. </p><p>“Actual” as well as “virtual” fractions of milling products were investigated comparatively. </p><p>Actual fractions were produced by mechanical screening whereas the virtual sizing was done by the MLA software.</p><p>The "virtual-sizing-approach" features a much simpler sample preparation procedure and considerably lower cost. It can be conveniently applied to intimately locked ores needing a fine grinding to a particle size distribution (PSD) below a "99%-passing-value" (P99) of 25 microns. However, its practical use is in dispute in terms of the reliability of the results.</p><p>Selected results are shown for a main gangue mineral (zircon) and the minor Y-mineral xenotime. </p><p>The influence of sample representativeness and particle counting statistics turned out to be of crucial importance. </p><p>From the results, it can be concluded that the virtual-sizing-approach can be used if grain counting numbers are high enough to ensure a variation coefficient below 20 %. This precondition is of particular importance in case of low-grade ores. </p><p>Given that all preconditions are met, grade-recovery curves, modal mineralogy, locking figures and even PSD trends can be read from virtual fractions. Prudence is recommended if the mineral recovery needs to be calculated for fractions.</p><p>The authors encourage processing engineers to use the virtual approach and offer further practical recommendations to verify and improve the reliability of the MLA results. </p><p>R. Gerhard Merker, Elpenrod, Sept 28th, 2015 R. Gerhard Merker - mineral processing engineer (MMP)</p><p>Fractions and head sample I minus 500, Cumulative mineral recovery of xenotime (with 95% mineral grade)</p><p>100</p><p>90</p><p>) Minus % (</p><p>500, real</p><p>.</p><p> c screen e</p><p>R 80</p><p> e m i t o n</p><p> e 70 X</p><p> e</p><p> v Minus i t</p><p> a 500, l</p><p> u virtual</p><p> m 60</p><p> u screen c</p><p>50</p><p>40</p><p>Fractions of head samples minus 500 microns, </p><p>Figure 1: Cumulative mineral recovery of Xenotime at a 95 % mineral grade after real and virtual screening</p>