deads

In mining, deads are the barren rock and waste material that surround a seam or body of ore. They have no economic value and must be removed, moved aside, or worked around to access the mineral deposit. The term is most common in hardrock mining, coal mining, and metallic ore extraction, where ore bodies are often embedded in larger volumes of worthless host rock.

The composition of deads depends entirely on the geology of the deposit. In a copper or gold mine, deads might be granite, schist, or other country rock with negligible metal content. In coal mining, deads are typically shale, sandstone, or mudstone that overlies or underlies the coal seam. The boundary between ore and deads can be sharp or gradational, and in marginal deposits, the distinction becomes a matter of economic cutoff grade rather than clear geology.

Deads create a major operational cost. They must be broken, loaded, and transported out of the pit or mine, consuming fuel, equipment time, and labor. In open pit mining, the ratio of deads to ore is called the stripping ratio: a 3:1 stripping ratio means removing 3 tonnes of deads for every tonne of ore. High stripping ratios make deeper parts of a deposit uneconomic to mine, even if ore grades remain adequate.

Disposal methods vary. Large open pit mines create separate waste rock piles, sometimes graded and compacted. Underground mines typically backfill worked-out areas with deads or store them at surface. Some deads are chemically aggressive, containing sulfides that oxidize and create acid drainage, requiring careful management to avoid environmental damage.

The word deads reflects practical mining speech: it is simply what is dead weight, carrying no value. The term contrasts with pay ore, live ore, or ore proper. In some regions and older texts, similar material is called waste or country rock, though deads remains the most common single term in active mining operations.