Dense Medium Separation
The dense medium cyclone (DMC) is the most ubiquitous of the DMS vessels in use, and deservedly so. It is efficient (when run properly), can process both coarse and fine sizes, and has a relatively small footprint. Unlike other forms of gravity concentration, it also makes a positive separation at a desired density cut-point, due to the presence of the medium whose density is easily controlled.
The beneficiation of pegmatite ore in the presence of other valuable minerals such as those containing tin and tantalum in addition to the lithium minerals increases the complexity of processing. This may in-volve additional operation to remove these minerals as by products. For example, in the treatment of Bernic lake pegmatite, spiral circuits are used to remove and concentrate tantalum minerals (Ferguson et al., 2000). Also, in the processing of Greenbushes’ pegmatite ore, the bulk flotation concentrate is treated with gravity separation techniques such as spiral and shaking table to remove heavy minerals, e.g., SnO2, Ta2O5 and Fe2O3 (Bale and May, 1989).
Dense media separation (DMS) or heavy media separation is a pre-concentration technique used to reject gangue minerals prior to grinding. DMS exploits the difference in specific gravity between the target and gangue minerals, and is commonly used in the separation of spodumene from other gangue silicates. The specific gravity of spodu-mene is between 3.1 and 3.2; this makes it slightly heavier than most gangue minerals such as quartz (2.65), albite (2.60) and muscovite (2.8). The spodumene, therefore, sinks while gangue minerals float in dense medium of appropriate specific gravity, and thus separated from each other.