The cylinder has many holes in it to allow undersized material (including gold) to fall into a sluice box.

The undersized material was blown to a cyclone separator that was mounted directly above the first Gallagher sampler.

The attritioned material is screened again to remove the oversizes "coarse rejects" with the undersized material returned to the plant.

In marine works, this segregation creates pockets of undersized materials that are easily eroded, and concentrations of large blocks that are transparent to wave action and provide windows for internal erosion.

After the pellets are screened, all undersized material is taken and sold as pellet chips and the onsize product goes to the pellet loadout via conveyor and out off the boomstacker into the pellet bowl.

Physical size separation is achieved as the feed material spirals down the rotating drum, where the undersized material smaller than the screen apertures passes through the screen, while the oversized material exits at the other end of the drum.

Screening efficiency is defined as the comparison of the undersized materials brought on the screening and discharged oversized product in contrast to the original amount of undersized materials in the feed stream.