Cornish mining slumps in 1870s
By the mid-1870s, mining Cornish minerals, particularly tin and copper, had become relatively uneconomic following the discovery of comparable mineral deposits in South Africa, South America and Central America (Mexico). As a result, some of the other local industries that prospered during the heyday of Cornish mining, such as rope-making, brick-making, mine-to-harbour haulage, and—to a lesser extent—the manufacture of explosives and safety fuses, were severely affected by the downturn in Cornish mining. 

Hard-rock miners sought after
Unable to compete on price, Cornish mines closed down and there was a mass migration of miners to the newly discovered mineral deposits in South America, South Africa and Mexico, where there was a high demand for, among other workers, skilled hard-rock miners from Cornwall and Germany. The pay cheques of Cornish miners working abroad helped sustain impoverished Cornish communities, and "kept poverty at bay for many families".