The existence of important copper deposits in Katanga had been known for a long time following a preliminary scientific assessment by the Belgian geologist Jules Cornet during an expedition in 1891. However, at the time, Katanga was too isolated to consider industrial exploitation of the copper deposits that he identified despite their importance. The Union Minière of Haut-Katanga (UMHK - Miner Union of Upper Katanga) was founded on the 28 October 1906 by different players including the Société Générale de Belgique, which also became involved for the first time in the economy of the Congo. Even though the first ingot of copper was poured in 1911, it was around four years later in 1925 that industrial exploitation reached full capacity.
The UMHK employed a growing number of African workers: 8,500 in 1919, 17,200 in 1929. Such a considerable expansion in a lightly-populated province, led the company to carry out massive recruitment outside Katanga, in Rhodesia at first, then in other regions of the Congo. To facilitate recruitment and encourage its workers to sign longer-term contracts, the management of the Union Minière implemented a paternalistic policy from 1926 onwards.
On the 1 January 1967, the assets of the UMHK in the Congo (including its participation in companies established in the Congo) were nationalized. They were transferred by the Congolese government to a new registered Congolese company, the Gecomin (General Company of Congolese Minerals), which thereafter became known under the name of the Gecamines.