Michigan used to be very abundant in copper, but recently a long term resource rush used up most of the state's copper resources. Michigan also used to have a great store of iron ore in Lake Superior, but that resource too has become too difficult to mine, and has a very limited profit margin.
Michigan has a large salt bed not too far under the surface of the lower penninsula, called the Salina Formation. Utilizing gas deposits, Michigan had a natural gas self-sufficiency of 25% in 1999.
The Great Lakes compose about 90% of the freshwater supply in America, and Michigan has juridiction of over 40% of the Great Lakes.
Mining dune sand is a profitable business in Michigan. Dune sand is used by the foundry industry for producing molds and cores and the construction industry for fill. Glass is manufactured from high quality dune sand, as is certain types of sandpaper.
Michigan's farms encompass about 30% of the state's land area.
The 19.3 million acres of forest take up more than half of Michigan's land area. As such, sustaining a lumber industry, and creating hunting organizations are pursuable practices in Michigan.