Ch. 5— Mining and At-Sea Processing Technologies • 187 



Figure 5-14.— Technologies for Processing Placer Mineral Ores 



Screening 



and 



sizing 



Gravity 

 separation 



Waste 

 (tailings) 



Hydrocyclones 



or 



heavy medium 



separation 



or 



or 



* 



Riffle tables 



* 



Drying 



11 ^- 



r^ fiuore 



-ray 



fluorescence 



sorter 



. . Gold 



Concentrates pjatmum 



°' Tin ore 



(finir 



Refining 



Metallic 



Gold 



Platinum 



Tin 



Drying kiln 



Magnetic 

 separation c: 



* 



Uncut 

 diamonds 



I 



Electrostatic . 



separation "^^tx 



V 



Tailings 

 (waste) 



V 



llmenite Rutile 



To pigment 

 manufacture 



* \ 



Zircon 



Other byproducts 

 Monazite etc. 



Offshore screening, sizing, and gravity separation may be adopted to reduce the amount of mate- 

 rial that must be brought to shore. Drying and magnetic and electrostatic separation steps will 

 most likely take place ashore. 



SOURCE: Office of Technology Assessment, 1987. 



in processing ores containing mineral grains of vari- 

 ous sizes is usually size separation. 



Size separation may be needed to control the size 

 of material fed to other equipment in the process- 

 ing stream, to reduce the volume of ore to be con- 

 centrated to a minimum without losing the target 

 mineral(s), and/or to produce a product of equal 



size particles. Separation is accomplished by use 

 of various types of screens and classifiers. Screens 

 — uniformly perforated (and sometimes vibrating) 

 surfaces that allow only particles smaller than the 

 aperture size to pass — are used for coarser materi- 

 als.'^ The size of screen holes varies with the ma- 



^Ibid. 



