text: Near Eastern development of bronze technology spread across Central Asia by way of the Eurasian Steppes, and with it came the knowledge and technology for tin prospection and extraction. By 2000 to 1500 BC Uzbekistan, Afghanistan, and Tajikistan appear to have exploited their sources of tin, carrying the resources east and west along the Silk Road crossing Central Asia. This trade link likely followed an existing trade route of lapis lazuli, a highly prized semi-precious blue gemstone, and chlorite vessels decorated with turquoise from Central Asia that have been found as far west as Egypt and that date to the same period.
  In China, early tin was extracted along the Yellow River in Erlitou and Shang times between 2500 and 1800 BC. By Han and later times, China imported its tin from what is today Yunnan province. This has remained China's main source of tin throughout history and into modern times.
  It is unlikely that Southeast Asian tin from Indochina was widely traded around the world in ancient times as the area was only opened up to Indian, Muslim, and European traders around 800 AD.
  Indo–Roman trade relations are well known from historical texts such as Plinys Natural History' (book VI, 26), and tin is mentioned as one of the resources being exported from Rome to South Arabia, Somaliland, and India.