Underground hard rock mining refers to various underground
mining techniques used to excavate
hard minerals, mainly those containing
metals such as
ore containing
gold,
silver,
iron,
copper,
zinc,
nickel,
tin and
lead, but also involves using the same techniques for excavating ores of
gems such as
diamonds. In contrast
soft rock mining refers to excavation of softer minerals such as
salt,
coal, or
oil sands.