2. Mineralurgical treatments

2.1 Preconcentration

In the case of tin ores, pre-concentration can be used to remove as quickly as possible a large mass of rejects that are sufficiently low in tin to be considered definitive. In fact, alluvial ores contain an abundant quantity of clay, as well as sterile quartz-based sands and gravels, so that overhead settling and gravimetric concentration by jigging seem a priori essential: the former to release the cassiterite embedded in the clay and eliminate it in the wash water, the latter based on the large difference in density between cassiterite (6.8 to 7.1 g/cm ³ ) and the main minerals in the gangue (around 2.7 g/cm ³ ).

On the other hand, in the case of...