Most notoriously, "Sovromcuarț" (or "Sovromquarțit"), while ostensibly producing quartz, as its name suggested, was in fact engaged in the extraction of uranium ore. "Sovromcuarț" started operating in 1950 at Băiţa mine in Bihor County, with a workforce of 15,000 political prisoners. After most of them died of radiation poisoning, they were replaced by local villagers, who did not know what they were mining. In secrecy, Romania delivered 17,288 tons of uranium ore to the Soviet Union between 1952 and 1960, which was used, at least partly, in the Soviet atomic bomb project. Uranium mining continued until 1961. All ore was shipped outside Romania for processing, initially to Sillamäe in Estonia; the uranium concentrate was then used exclusively by the Soviet Union.