![[photo, Caterpillar bulldozer & conveyor belt dumping coal, Conrail coal yard, Baltimore, Maryland]](/msa/mdmanual/01glance/economy/images/1198-1-07110b.jpg)
In 2013, nearly 400 mines were active in the State. Some 63 firms operate mines in Maryland, according to the 2007 U.S. Economic Census. With a combined payroll of $62.7 million, they employ nearly 1,300 people.
Caterpillar bulldozer & conveyor belt dumping coal, Conrail coal yard, Baltimore, Maryland, May 2015. Photo by Sarah A. Hanks.
By the mid-1900s, the mining industry began to decline in Maryland. More buildings were being constructed with brick, crushed stone, and steel. This factor, as well as a decrease in reliance on coal as a fuel source, caused many mines to became less profitable. Some tapped out; others became financial burdens on owners. Consequently, fewer mines were dug, and more closed.
As many mines were abandoned, they posed safety and environmental risks. Plans and programs to reduce risks and improve former mine sites are overseen by the Mining Program within the Maryland Department of the Environment, and the Interstate Mining Compact Commission.
Drift Mines use horizontal passages to access mineral deposits, when the mineral is located close to the surface, and the vein forms a nearly horizontal sheet.
Shaft Mines employ vertical tunnels to reach far below the surface. They are used when a mineral forms a vertical vein, or lies too deep to reach by other means.
Slope Mines use sloping access shafts to reach mineral deposits. They afford access to minerals not found at the surface, but not deep enough to warrant shaft mining.
Surface Mines extract minerals that are just below the surface, or are too unstable for tunnelling techniques to reach. The term, surface mining, describes all procedures that remove the surface to reach mineral deposits. This method includes open-pit and strip mining, and is used to reach cinder, gravel, and sand.
COAL MINES
Coal mines have been a major source of income for Maryland since the early 1800s. Found in the western counties, these mines once exported to all states, and even Europe. Coal mining here peaked in the early 1900s with more than 450 mines in operation, producing over five million tons a year. In the years since, despite a dramatic drop in the number of active mines, technological advances have allowed the production of more coal per mine with less damage to the environment than ever before.
Today, within the Department of the Environment, the Bureau of Mines oversees and approves all proposed mining plans in the State. The Bureau also evaluates and approves plans for environmental restoration of lands containing abandoned mines. Currently, 60 permitted coal mines operate in Maryland, producing over two million tons of coal each year. Most are surface mines, while five are underground drift mines.
NONCOAL SURFACE MINES
Noncoal is defined as any mined commodity that is not coal or peat, and is referred to as nonfuel or industrial minerals. Noncoal includes aggregate (used in blacktop, concrete, & plaster), clay, and stone, as well as other minerals.
There are 298 noncoal surface mines operating in Maryland. Most of them are found in southern Maryland - in Charles, Prince George's and St. Mary's counties. The Minerals, Oil and Gas Division within the Department of the Environment oversees these mines.
Mined stones are classified by two types: crushed, and dimension.
Crushed Stone is a form of aggregate, and is a base for making asphault, concrete, macadam, and tarmac. Used extensively to pave and construct roads, crushed stone mined in Maryland has increased in annual value from $161 million in 1997 to $209 million in 2011.
Dimension Stone is any stone that is mined, then altered to required specifications. Once used as a primary building material, dimension stone production has declined greatly over the last century. The value of dimension stone mined from Maryland in 2011 was $1.2 million, down from $2.4 million in 1997.
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