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 surfaces typically manufactured with standard materials (i.e., plastic, chrome, aluminum) were replaced with copper alloys. These included a copper alloy set of sink tap handles (60% Cu, 40% Zn) and a ward entrance door push plate (70% Cu, 30% Zn). Contamination reductions of 90–100% were observed for "Staphylococcus aureus", "Escherichia coli", "Klebsiella pneumoniae", "Acinetobacter baumanii", "Enterococcus" spp., and "Candida albicans" on the copper alloy surfaces versus the non-copper standard surfaces. A microorganism reduction of 100% was observed on the hot tap copper alloy handle. The high degree of clinical performance suggested that copper alloy surfaces may increase the effectiveness of