schlich

Schlich is the lightweight, fine fraction of crushed ore that remains in suspension or settles slowly when ore is processed through water-based separation methods. In gold, tin, and lead mining, schlich typically consists of particles finer than 200 mesh (roughly 75 micrometers), including both valuable minerals and waste rock, separated from the coarser, heavier material that sinks quickly. The term is dated but still encountered in older mining literature and in regions where traditional gravity separation persists.

The recovery of schlich depends on water's ability to carry fine particles while allowing dense material to drop out. In a typical wet crushing operation, ore passes through stamps or ball mills, then into classifiers or settling tanks where water flow is carefully controlled. Heavy minerals like cassiterite (tin oxide) or native gold settle in the bottom fraction, while schlich, lighter silicate minerals mixed with some valuable ore, remains suspended and must be caught separately, often by panning, tabling, or sluicing before it exits with the tailings water.

The boundary between schlich and true tailings is not sharp; much depends on classifier efficiency and water velocity. Fine schlich particles, especially those below 100 mesh, are easily lost to overflow. Historically, recovery of schlich was labor-intensive, relying on hand panning or simple gravity tables. In some operations, schlich was returned to the mill for reprocessing, while in others it was discarded, representing a real loss of recoverable metal. Modern hydrocyclones and spiral separators have partly replaced schlich recovery with continuous classification, though the principles remain the same.

The word itself is German, reflecting the dominance of German mining engineering terminology in the nineteenth century. Schlich appears most often in tin-mining accounts from Cornwall, the Erzgebirge, and Southeast Asia, where alluvial and weathered ores produced abundant fine fractions. Its use has declined as flotation and other concentration methods became standard; these processes treat ore as a whole rather than separating by particle size alone.

Understanding schlich is useful when evaluating historical mining accounts, assessing old tailings for potential reprocessing, or troubleshooting gravity separation circuits. The presence of schlich in overflow indicates either poor classifier tuning or recovery of genuinely fine-grained ore minerals, a distinction that affects both operational decisions and resource estimates.