History of Silmet dates back to 1926 when Swedish-Norwegian Eestimaa Õlikonsortsium (Swedish: Estländska Oljeskifferkonsortiet; English: Estonian Oil Consortium), controlled by Marcus Wallenberg, was established to build a shale oil extraction plant in Sillamäe.

However, due to the Great Depression, production halted in 1930 and was restarted only in 1936 by the reorganized consortium called Baltic Oil Company.

During the subsequent German occupation, the plant was restored and subordinated to a company named Baltische Öl GmbH.

Restoration of the plant restarted immediately after Soviet troops took control in Estonia in 1944.

In 1946, the Council of Ministers of the Soviet Union approved the establishment of the diversified enterprise Kombinat No 7 on the basis of the Glavgastopprom Oil Shale Processing Plant for mining and processing Dictyonema argillite ore (a type of oil shale).

In 1947 when the new factory was built, the code name Military Unit No 77960 was assigned to the Kombinat No 7.

[2][4][5][6][7] Later richer uranium ores were imported to the Sillamäe plant from various locations of Central Asia and the Eastern Bloc, mainly from mines in Czechoslovakia, East Germany, Hungary, Poland and Romania.

[9] In 1970, the plant started to process loparite ore from the Kola Peninsula producing tantalum and niobium.

In 2005, Vähi sold a controlling stake in Silmet to Russian related Swiss company Zimal SA, but bought it back in 2010.