fell

Fell is the fraction of crushed ore that passes through a sieve mesh during primary classification. When run-of-mine ore is broken and screened, the material finer than the mesh opening flows through as fell, while coarser fragments are retained. This distinction matters because fell requires different handling and processing than lump ore: it tends to cake, pack densely, and behave poorly in subsequent stages if not managed carefully.

The size boundary between fell and screened product depends on the mesh specification chosen for the operation. A 10 mm screen, for example, might retain lump ore while fell passes below. Fell typically contains a high proportion of fines: clay, dust, and weathered mineral fragments. In iron ore operations, fell may be 20 to 40 percent of the total broken product, though this varies with ore quality and mining method.

Handling and recovery

Fell presents practical problems. Its small particle size creates dust during transport and storage, raising both environmental and occupational health concerns. The material's tendency to compact under its own weight can cause bridging in bins and chutes. Many operations treat fell separately: it may be agglomerated with binders and pelletized, or sent to a separate flotation or concentration circuit rather than following the main lump ore path.

The term fell reflects its origin in the smelting trades, where it denoted material that literally fell through the sorting meshes. In modern ore dressing, fell is no longer waste: recovery rates and downstream processing have improved enough that even fine fractions contribute value. However, the old name persists because it describes the mechanical outcome of the screening step itself, regardless of economic use.