By , Michigan was one of the leading producers of gypsum and for the last 40 years has ranked second among the states in domestic production. Although it was later discovered that slabs of gypsum used as building facings disintegrated rapidly after being exposed to the elements, this very softness made for easy carving into bowls, vases and sculpture.
In , this may have spurred William Powers to begin mining gypsum on his west-side Grand Rapids property. While his venture into a foot layer, 60 feet below the level of the riverbed, was short lived, the exact site of his "digs" aroused intense interest nearly 75 years later when the city became involved in urban renewal and redevelopment along the riverbank.
By the late s, the horse-drawn mine cars of a previous era were gone. Gone also were the associated mushroom industry, which flourished in the dark dampness beneath a layer of fertilizer supplied by the horses.
In , the Alabastine Mining Company mine in Wyoming, which had recently closed, gave rise to an entirely new enterprise. Originally used to store foods such as eggs, nuts, cheese and potatoes, the facility today, grown to 45, square feet and equipped with temperature and humidity controls for specialized storage needs, provides a safe and comfortable home for microfilm and computer records as well as food. The room and pillar mining method leaves considerable rock in place as a natural support.
Ventilated by fans that circulate fresh air, the rooms and tunnels are about feet below the surface. Diesel-operated machines drill a specific pattern of blast holes in the end of each working side tunnel or "bench. Current mine output of about tons per day requires only two maintenance workers and a production crew of five.
Over the years, Michigan has consistently ranked first or second in the United States in production of gypsum, and the deposits are vast. This versatile mineral touches our lives every day and promises to be an important part of our future.
As the seas receded and evaporated, rock and mineral deposits such as halite rock salt , gypsum calcium sulfate with water , liquid brines, petroleum, lime, clay, sandstone and coal were left behind. Gypsum is a non-metallic mineral, found in rock form. It is composed of Chemists call it Hydrous Calcium Sulphate, and as there is one molecule of calcium sulphate combined with two molecules of water. It has the chemical formula CaSO 4 2H 2 0.
This water however, is perfectly dry, and is known as "water of crystalization". It could be compared with ice, which, too is water in crystaline form, but there is this an important difference; ice will melt, or change to water, when it is exposed to a to temperature above 32 F.
Water of crystalization, in gypsum, does not change until it is subjected to heat above F but at that temperature the water of crystalization changes form and becomes water vapor and is driven off from the gypsum just as steam is driven off from water at F. Gypsum, an evaporite rock, formed at the base of the shallow Michigan basin as it dried up, leaving the CaSO 4 H 2 O deposits behind, as gypsum. In absolutely pure form, gypsum is white.
However, gypsum normally contains impurities whose presence makes the rock appear gray, brown, pink, or even almost black. Gypsum deposits lie in flat beds of about six to eight feet in thickness, and are often inter-layered with limestone or shale. Gypsum deposits were formed millions of years ago when salt water oceans covered most of the earth, and as they receded, may inland "dead" seas were formed which, as evaporation continued, became more and more salty.
As those salts precipitated, they formed various compounds in turn, one of which was gypsum. As millions of years passed, these salt deposits combined with decayed vegetation and other minerals, and eventually the result was stratified rock, with layers of gypsum and layers of limestone alternating, the whole covered over with many feet of glacial deposits.
Gypsum is produced commercially from open pit quarries near Tawas City and Alabaster in Iosco county and from underground mines near Grand Rapids. Gypsum deposits are located in the center of the Michigan basin. It is only mined at places where the gypsum is near the surface, while at others it is buried by more than feet of rock see map below. Gypsum beds are seldom more than 20 feet in thickness. Near Grand Rapids, gypsum of the Michigan Formation are mined extensively, for they are very near the surface in that area.
Gypsum is commonly associated with rock salt and sulfur deposits. It is processed and used as prefabricated wallboard or as industrial or building plaster, used in cement manufacture, agriculture and other uses. In the United States, gypsum is mined in about 19 states. Over 30 million tons of gypsum is consumed in the United States annually. Canada, Mexico and Spain are other significant producers of raw gypsum. In all, more than 90 countries produce gypsum.
In most open pit gypsum operations, benches are drilled and blasted using ammonium nitrate as the explosive. Because gypsum is so soft, most drills can drill through it at a rate of roughly 23 ft per minute. From here, the plaster leaves the British Gypsum plant and is sent to merchants and distributors across the UK, ready for plasterers to buy.
Once the plasterer mixes the product with water, it will return back into its original state, creating a plaster finish for their project. Do you have any questions about the mine to merchant process? Tweet us! There are no comments yet, be the first to share your thoughts. Login Close.
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