Tin mining to trace metal content in the copper ore It was soon discovered that the addition of tin or arsenic to copper increased its hardness and made casting much easier, which revolutionized metal working techniques and brought humanity from the Copper Age or Chalcolithic to the Bronze Age around 3000 BC. Early tin exploitation appears to have been centered on placer deposits of cassiterite. The first evidence of tin use for making bronze appears in the Near East and the Balkans around 3000 BC. It is still unclear where the earliest tin was mined, as tin deposits are very rare and
Antimicrobial copper-alloy touch surfaces in rooms with copper touch surfaces were significantly lower than in rooms without copper surfaces. "Staphylococci" were the most predominant microorganism isolated and copper was effective in reducing the "Staphylococci" microbial burden. Further studies regarding the clinical implications of copper's intrinsic ability to reduce microbial burdens in hospitals are being planned. Researchers from the Kitasato University School of Medicine conducted antimicrobial studies of "S. aureus", "E. coli", and "P. aeruginosa" on various Japanese copper alloy coins and on copper alloy plates. The microbes were strains from hospital environments. Copper and its nickel-silver, cupronickel, and brass alloys were found to kill