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 April 2011 analyzed the effectiveness of copper-alloy furnishings to lessen the microbial load on various frequently touched surfaces such as door handles, toilet seats, and railings. Of the 14 surfaces tested 8 had statistically significant decreases in the number of microbes found on them while the other 6 had a decrease in the number of microbes as well, but not in a statistically significant amount. Additionally certain microbes in particular were found in far less quantities on the copper-alloy surfaces than on the normal ones, these being Vancomycin-resistant "Enterococcus", "Staphylococcus aureus", and Coliform bacteria. The study concluded that copper