wring

In mining, a lode wrings when its ore content falls below economic extraction thresholds. The vein does not vanish; rather, assay values drop to a point where processing and haulage costs exceed revenue. A miner might say a shaft has wrung out, meaning the zone that once yielded profitable metal now yields only marginal waste or low-grade material. This is distinct from genuine geological exhaustion, since future price movements or technological advances in concentration can revive a wrung-out section.

Wringing typically follows a predictable pattern in a working lode. Early stages yield high-grade ore near the surface or in structurally rich pockets. As mining progresses deeper or laterally along the vein, ore widths narrow and metal values per ton decline. A miner removes the rich material preferentially, leaving behind zones where grade has dropped by half or more. At some point, each working face or stope reaches what engineers call the economic cutoff grade: the minimum gold, copper, or silver content per ton that justifies extraction.

Naming and context

The term wrings carries an evocative sense of exhaustion. Just as wringing a cloth removes the last moisture, wringing a lode extracts its last saleable metal. The word appears in mining literature from the 19th century onward and remains standard in hard-rock mining operations. It applies to metalliferous veins more often than to coal seams, though coal operators may speak of a seam pinching out rather than wringing.

A wrung lode does not necessarily mean permanent closure. Many old workings were re-entered decades later when metal prices rose, grade-recovery methods improved, or costs fell. Conversely, a lode may wring in one sector while remaining productive elsewhere along its strike. Miners often mark these boundaries carefully: a section wrung at 2 grams per ton gold in 1987 might become viable again at 4 grams per ton in a bull market, or workable at 1.5 grams per ton if a new mill achieves better recovery.

The transition from productive to wrung is not always clean. A working face may have erratic grades: one day rich enough to justify extraction, the next day too lean. Miners manage this through selective mining or blending, mixing high-grade and low-grade material to maintain an average above cutoff. Once a zone consistently falls below cutoff across its full width and length, it is said to have wrung, and mining effort shifts to fresher ground.