## 4 Conclusions  
This study shows how medium-grade celestine mineral from Montevive can be efficiently concentrated using dense media separation (DSM) with a laboratory scale hydrocyclone system. The influence of relevant operation parameters such as conditioning celestine mineral, type of dense medium, and feed pressure were tested. These results could be used to scale up the process to a semi-industrial and industrial scale. This would enable the mine operation to become more sustainable and decrease its overall impact on the environment.  
In the case of ferrosilicon media (CG, F, C40), the stability of the suspension increases as the grain size decreases. The addition of magnetite increases the stability of the suspension (FM) (even though magnetite has a larger particle size than ferrosilicon) due to their non-spherical shape. Moreover, dense media rheological and stability properties are highly variable and should be regularly monitored during the separation process.  
The optimum results for the celestine mineral concentration experiments were obtained in the under stream for the coarse fraction of the mineral (>250 \(\upmu\)m). If only considering the output under stream (UNDER), and the coarser (UH) and smaller (UL) size fractions, the optimum results (highest celestine mass recovered) were obtained using the run-of-mine mineral (without desliming) and CG, F, or FM media.  
If examining the celestine concentration alone, the optimum results were obtained when the C40 medium was used, which recovered mineral with up to 90% celestine content. However, although the C40 medium achieves high concentrations of celestine, the output flow rates and the total mass of celestine recovered are low.  
Further studies are needed to validate the parameters of dense medium density and hydrocyclone inlet pressure on a semi-industrial scale, as well as to study the hydrocyclone inclination parameters.  
Figure 9: Quantities of celestine recovered in the different output streams for the different media tested.  
**Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app131810206/s1](https://www.mdpi.com/article/10.3390/app131810206/s1)]([https://www.mdpi.com/article/10.3390/app131810206/s1](https://www.mdpi.com/article/10.3390/app131810206/s1)). Figure S1. Conditioning; Table S1. Interest elements content in FeSi; Figure S2. Stability test plot; Table S2. Physical properties of FeSi; Figure S3. Schedule of AMP test equipment; Table S3. Particle size of atomised FeSi; Figure S4. AMP Test equipment; Table S4. Element content in magnetite; Figure S5. Magnetic separator; Table S5. Particle size of magnetite DMS80; Figure S6. Bar Graph of mineral phases in each output stream: Table S6. Viscosity and stability of dense media applied; Figure S7. Setup schedule of celsestine degree (run-on-mine): Table S7. Theoretical and empirical weights; Table S8. Obtained mass of each stream; Table S9. XRD analysis and flow rate of output streams.  
**Author Contributions:** N.A.-R., methodology, investigation, writing--original draft, writing--review and editing; A.B.R.-N., methodology, formal analysis, validation, writing--review and editing and funding acquisition; M.C.d.H., validation, writing--review and editing, supervision; M.J.M.-B., conceptualization, formal analysis, writing--review and editing, supervision and funding acquisition. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by CNT 5589 (University of Granada) and MineTheGap (European Union) CELABDEN PROJECT.  
**Institutional Review Board Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** Advanced Mineral Processing (AMP) provided images/schematic of the pilot plant to create Figure 1B.  
**Conflicts of Interest:** The authors declare no conflict of interest.