Commercially, selenium is produced as a byproduct in the refining of these ores, most often during production.
Occupational exposure to the oxide occurs at production sites, during processing and refining of vanadium ores and sludges, during manufacturing of vanadium-containing products, in the course of combustion of vanadium-rich fuels, and by handling of catalysts in the chemical industry (Plunkett 1987).
He also visited Freiberg, in Saxony, observing the smelting and refining of lead ore.
They too are now exhausted, but the refining of imported metallic ores remains an important component of Belgium's economy.
Selenium is commercially extracted as a byproduct in the refining of metal sulfide ores, most often during copper production.
The affinity between mercury and gold and silver was noted during Roman times and described in 1540 (Agricola 1950; Nriagu 1994), and the technique of mercury amalgamation, which enables the refining of lesser quality ores than is possible with smelting, first came into industrial use for silver refining in New Spain (present-day Mexico).
The main works in the mine were classified as mining, dressing of ores, refining, and clerical work.
Commercially, however, thallium is produced not from potassium ores, but as a byproduct from refining of heavy metal sulfide ores.
As a consequence, cadmium is produced mainly as a byproduct from mining, smelting, and refining sulfidic ores of zinc, and, to a lesser degree, lead and copper.
It is generally produced commercially as a by-product in the refining of copper, and nickel ores.
