Hard-rock mining has taken place in the province for over 130 years (as of 2012). The mining industry in Ontario produces more than 30 different metal and non-metal mineral products, and is responsible for a major percentage of Canada's nickel, gold, copper and platinum-group metals production. The extraction of metallic minerals is concentrated in Northern Ontario, while the southern portion of the province produces salt, gypsum, lime, nepheline syenite and structural materials (sand, gravel, stone), along with some petroleum. As of 2014, the mining industry produced about $11 billion worth of minerals. Derisory fees are charged by the government for prospecting licences ($25.50) and exploration permits (nil), in keeping with the duty of economic development of the province. The exploration permit process is meant as a means to notify interested parties, such as surface landowners, of the activities of miners. The development of a mine proceeds through "advanced exploration" to "production" status, the legislation for which is detailed in the Mining Act of Ontario; this covers hard-rock, aggregate, diamond and petroleum mines.