Due to the variability and complex nature of REE-containing ores, it is vital to understand the mineralogical characteristics, before embarking on any metallurgical testwork campaign. REE's are present in a variety of phases/minerals, all of which may react differently during processing. It is therefore important to identify and quantify all the REE-phases present in the ore, their mineral associations, grain size distributions as well as their liberation characteristics. In order to quantify the elemental deportment of the different REE's into the different REE-bearing phases, it is necessary to determine the mineral chemical compositions by Electron Microprobe. By assigning the average measured REE-elemental compositions to the different REE-phases, it becomes possible to determine the amount of each REE per REE-phase. Predictions about the best theoretically achievable grades and recoveries can be made. The data obtained are used to design a metallurgical testwork program suitable for the specific ore-type. (C) 2013 Elsevier Ltd. All rights reserved.