The Romans used hydraulic mining methods on a large scale to prospect for the veins of ore, especially a now-obsolete form of mining known as hushing.They built numerous aqueducts to supply water to the minehead.Although they had over 20,000 slaves working them, their technology was essentially identical to their Bronze Age predecessors.
The mines at Grimes Graves and Krzemionki are especially famous, and like most other flint mines, are Neolithic in origin (ca 4000–3000 BC).
However, it was the Romans who developed large scale mining methods, especially the use of large volumes of water brought to the minehead by numerous aqueducts.
The water was used for a variety of purposes, including removing overburden and rock debris, called hydraulic mining, as well as washing comminuted, or crushed, ores and driving simple machinery.
Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay.
Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory.