The performance of the unitswas heavily dependent upon the efficientremoval of fine root matter in the screeningprocess. The Reichert conehad low installation and operating costs due tohigh tonnage per m2 of floor area and fewmoving parts. Variable slots were alsoemployed and these were automated and usedin grade control algorithms. Reichert cones used incleaning duties were of the double, single,single (DSS) type allowing further upgradingof the concentrates. The tailings from the double andsingle stages were fed onto the next doublestage and the process repeated (see Figure 2).Dilution water was fed to each of the singlecones at a rate of approximately 7 m3/h (28m3/h for 4DS unit). Heavy particlesseparated to the bottom of the film as theslurry flowed towards the centre and concen-trates were removed through an annular slot(tulip) and fed onto a single cone for furtherupgrading. Slurried feed wasdistributed around the periphery of the conesurface and fed to two separation surfaces viaa mouth organ splitter. Reichert cones are high capacity flowingfilm concentrators. The primary units werefed at a rate of 80 tph and a density of 60%solids by weight. The deposit was mined using two dredgesfeeding a floating 2 000 tph concentrator.Concentrator feed was screened and fed to twofour-stage circuits consisting of primary,scavenger, cleaner and recleaner Reichertcones (see Figure 1). Orebody contained a greater proportion of non-valuable magnetic heavy mineral in the SGrange of 3 to 4 compared to West Australianand Florida USA deposits, making mineralseparation more difficult1.

Richards Bay Minerals (RBM) first miningconcentrator and mineral separation plantcommenced operation in 1977 to processilmenite, rutile and zircon bearing dunaldeposits along the northern Natal coast. This paper discusses the history ofgravity separation at Richards Bay Mineralsand briefly comments on future developments. Just as the gravity separationindustry evolved, Richards Bay Minerals alsoevolved in their use and approach to gravityseparation. Reichert tray systems for pilot-scale 2.0- and 3.Gravity separation techniques have been inuse in the mineral sands industry for decades from the Reichert cone to Wilfley tables,Wright sluices and the Kelsey Jig, allattempting that elusive perfect gravityseparation.Wilfley, Deister, and Gemeni shaking tables.Variable-speed controls, automatic samplers, rate-monitored process water, and agitated interstage storage tanks complete the facilities. Samples as large as several tons can be fed continuously, either wet or dry, to the different concentrating units. The pilot-scale facilities are equipped to handle a variety of test programs on a larger scale.

Preliminary closed-circuit tests can be made with as little as a few kilograms of feed material. Our laboratories contain small jigs, shaking tables, a Knelson concentrator, a Mozley vanner, and heavy-media separation equipment. Hazen's gravity concentration facilities are among the finest in the world. This technology can be applied to primary recovery, preconcentration, and final upgrading, as well as recycling and soil washing. Gravity separation, relies on the difference in density of the mineral and the gangue.

Wet gravity circuit