Resource potential of REE as by-product of an existing mining operation – A geometallurgical assessment

A systematic geometallurgical study of the rare earth mineralogy and beneficiation potential as by-product was performed, based on a currently operating flow sheet of an existing large-scale industrial mining and beneficiation operation. For this purpose, a representative suite of samples was collected from a single mining block prior to blasting. The material derived from this mining block was then tracked through beneficiation by comminution and a sequence of flotation steps. Samples were collected at all crucial steps of the beneficiation plant. Whole rock geochemical analyses and quantitative mineralogical and microstructural analyses (by MLA), complemented by mineral chemistry data for relevant REE minerals, were obtained for a suite of more than 60 samples. These data were then used to assess the deportment of REE and to track the route of REE-minerals within the beneficiation process.
Apatite was found to be the most important primary host mineral for REE. Postdepositional alteration evidently led to the breakdown of apatite, resulting in the formation of microcrystalline xenotime and monazite of secondary origin. The latter are the two most abundant rare earth minerals identified in the mining block studied. Additionally identified rare earth minerals occur only in minor or trace amounts. Other minerals were found to contribute only limited amounts to the total REE content of the ore.
Process samples from the flotation circuit illustrate that the material from the cleaner circuit tailing, being usually considered as waste, is strongly enriched in monazite and xenotime, i.e., the two most common REE minerals. The REE minerals are well liberated, thus leading to the conclusion that it may be feasible to produce REE minerals as a future by-product by only slight modification of the current flow sheet.