Mining in Tanzania in the modern era dates back over one hundred years, first under German colonial rule; during the First World War a number of military engagements took place there. After the war ended control of the area was ceded to the British, under whose colonial authority mining and other activities continued and expanded. Mining focused on gold, diamonds and a variety of colored gemstones, notably including the discovery and development of the world's largest diamondiferous kimberlite pipe (to date), by Canadian geologist John Williamson, a deposit that remains in production to this day. Shortly after achieving independence from the British, in 1961, Tanzania veered left, leading to the nationalization of most private sector industries, in turn resulting in the inevitable a mass exodus of foreign investment and private capital and the consequent decline in economic activity in all sectors, including mining. Finally, beginning in the 1990's, in line with many other developing countries around the world, the Tanzanian government instituted several reforms to return to a free market economy, privatize the mining industry and encourage both domestic and foreign investment in all economic sectors. In the case of the mining industry, this was supplemented, in 1998, through the passage of a new, industry friendly mining code.