Michigan’s mineral resources are varied. They include cement, iron ore, petroleum, natural gas, salt, and gypsum. The state’s production of iron ore is second in the nation, behind only that of Minnesota. Michigan is the leading state in the production of magnesium compounds and the second leading state, behind Florida, in the production of peat, which is marketed for fertilizer, not for fuel. Among the stones that are extracted are limestone and such gemstones as thomsonite, greenstone, datolite, agate, and a fossil coral called Petoskey stone. By the mid-1970s nonmetals, including construction materials and saline minerals, had become more important than metals in the state’s mineral output. Mineral fuels also became much more significant in the 1970s.
Commercial mining for copper began in the 1840s, and soon afterward, copper fever engulfed the Keweenaw Peninsula. During the next 40 years about half the nation’s copper came from Michigan mines. Other areas with larger deposits later surpassed Michigan in copper production. However, the state still has some of the nation’s purest deposits. With the closure of the White Pine mine in 1995, no commercial mining of copper remained in the state. In the mid-1990s White Pine was experimenting with electrolytic refining and acid solution mining in portions of existing mines, with the hope that the process would allow the resumption of commercial production. In 1996 citizen protest and a review by the U.S. Environmental Protection Agency of the solution mining process effectively halted this pilot program.
Iron ore has long been one of the leading minerals mined in Michigan. Originally there were three iron-ore ranges in the state, all in the Upper Peninsula.
The Marquette Range in Marquette County was the leading producer, followed by the Menominee in Iron and Dickinson counties and the Gogebic range before its plants closed in the late 1960s. The Menominee and Gogebic ranges extend into Wisconsin and are part of the Lake Superior ore district, from which Minnesota also extracts iron ore. The Superior ores were long noted for their high quality, but the ores have run out.
In the late 1950s the Superior ores encountered stiff competition from high-grade imported ores, chiefly those from the Labrador-Québec mines and from Venezuela. Within a few years ore companies began to process the lower-grade ores, such as taconite in Minnesota and jaspilite in Michigan. The processing, called beneficiating, removes the useless material and concentrates the ore into pellets that are highly efficient for blast-furnace steelmaking. The pelletizing process gave a temporary boost to the industry, but production began to level off in the late 1960s. No ore was mined in the Gogebic Range after 1967. By 1970, several of the pellet plants had closed or had suspended operations. In 1982 the Groveland mine in the Menominee Range and its pellet plant were permanently closed. In 1996, 15 million metric tons of pellets were produced at two remaining plants.
Most of Michigan’s iron ore is shipped by rail and then by water through the locks at Sault Sainte Marie to Detroit and other large steel centers. A large oil and natural gas field was discovered in 1969 in the northern part of Michigan’s Lower Peninsula. In 2006 production amounted to 5 million barrels of crude petroleum and 8 billion cu m (265 billion cu ft) of natural gas. While production of natural gas was increasing, the amount of oil being pumped was substantially less than in the mid-1980s.
Limestone is the most abundant and valuable of the stones mined in Michigan. It is used primarily as a flux in the steelmaking process and in the chemical and construction industries. Major deposits are found along the northwestern and northeastern shores of the Lower Peninsula. The manufacture of portland cement is based on native limestone and is one of the state’s leading mineral products. Lime, which has a number of industrial uses, is produced primarily in Wayne County. The Lower Peninsula, with abundant supplies of sand and gravel, provides the state with basic materials for its construction industry. Gypsum, used locally in the manufacture of wallboard, exterior sheathing, lath, and plaster, is mined in the Grand Rapids area and quarried at Alabaster. The state is a leading salt producer. Salt is mined in the Detroit area, where there are vast underground deposits. It is also obtained from brines in the central Michigan area around Midland, Saginaw, Bay City, and Whitehall. Natural salines, including bromine, calcium chloride, calcium-magnesium chloride, other magnesium compounds, and potash, are also extracted from brines in the Lower Peninsula. "Michigan" © Emmanuel BUCHOT, Encarta, Wikipedia
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