Tin sources and trade in ancient times Bantu culture of Zimbabwe are known to have actively mined, smelted and traded tin between the 11th and 15th centuries AD . Tin deposits exist in many parts of South America, with minor deposits in southern Peru, Colombia, Brazil, and northwestern Argentina, and major deposits of exploitable cassiterite in northern Bolivia. These deposits were exploited as early as 1000 AD in the manufacture of tin bronze by Andean cultures, including the later Inca Empire, which considered tin bronze the "imperial alloy". In North America, the only known exploitable source of tin during ancient times is located in the Zacatecas tin
Antimicrobial copper-alloy touch surfaces microbes relatively rapidly – often within two hours or less – and with a high degree of efficiency. These antimicrobial properties have been demonstrated by an extensive body of research. The research also suggests that if touch surfaces are made with copper alloys, the reduced transmission of disease-causing organisms can reduce patient infections in hospital intensive care units (ICU) by as much as 58%. Copper alloy surfaces have intrinsic properties to destroy a wide range of microorganisms. In the interest of protecting public health, especially in healthcare environments with their susceptible patient populations, an abundance of peer-reviewed antimicrobial efficiency studies