박테리아 광부들
과학동아 1990년 08호
gold, silver, copper and iron, but newer metals discovered only in modern times. Nickel, cobalt, tungsten, manganese, chromium, vanadium, niobium and so on, all had their valuable uses.High concentrations of the necessary ores were dug up and smelted. The metals were then used and, eventually, discarded as scrap. The highest concentrations were used up and metallurgists learned to used poorer ...