Crushed and Broken Limestone

Crushed limestone production is the largest of three related industries that extract and process nonfuel, nonmetallic minerals. Primarily employed as aggregate, which refers to a wide number of sand, gravel, and stone mixtures, crushed stone is an essential component of the U.S. infrastructure because of its use in the construction of highways, airports, river locks and dams, railroad ballast, and breakwaters. It is, however, considered a "high-volume, low-value commodity" with relatively stable prices since the 1970s, according to the U.S. Geological Survey (USGS).

The crushed stone industry is the largest nonfuel mining industry in the United States, with about 1,600 firms operating approximately 4,000 active quarries, 86 underground mines, and 311 sales and distribution yards in 50 states as of 2010. Limestone and dolomite accounted for the majority (70 percent) of crushed stone production and sales in the United States. The essential make-up of limestone is calcium carbonate (CaCo3). If 10 percent or more of magnesium carbonate is present, it is called "magnesian" or "dolomitic" limestone. The term "limestone" usually acknowledges the presence of dolomite.

After growing by an average of three percent in the late 1990s, crushed stone production began to decline in the early 2000s, falling by two percent to 1.49 billion tons in 2003. Growth resumed in 2004, reaching 1.63 billion tons; 2005 and 2006 saw small increases, with production rates of 1.70 billion tons and 1.78 billion tons, respectively. However, production fell again in 2007, this time to 1.65 billion tons, and the downward trend continued in 2008, dropping to 1.44 billion tons. With the economy in the midst of a deep recession, consumption dropped again in 2009, to an estimated 1.11 billion tons. Of the total crushed stone produced in 2009, approximately 83 percent was used as construction aggregates, mostly for highway and road construction and maintenance; 11 percent for cement manufacturing; two percent for lime manufacturing; two percent for agricultural uses; and two percent for special and miscellaneous uses and products. Recycling of crushed stone increased by 45 percent in 2009.

The slowdown in the U.S. economy continued to affect the industry into the early 2010s. Production of crushed stone in the first quarter of 2010 decreased 11 percent as compared to the same period in 2009. According to the USGS, the industry would continue to be influenced by both private and public sector activity. Although the economic slowdown led to a decline in consumption during the late 2000s, the multibillion-dollar stimulus package put in place by the Obama administration in 2009 to jumpstart to flailing economy set aside nearly $60 billion for highway infrastructure and other construction-related improvements. Although not sufficient to spur growth in the industry, the funds, which were expected to turn into actual onsite projects in 2010 and 2011, were expected to help hold afloat the industry during economically difficult times.

In the past, most crushed and broken stone was mined from open quarries. Recent trends favored underground mining. Underground room-and-pillar mines are operated on a year-round basis and do not require as much material removal. Additionally, underground mining requires less surface space and consequently avoids the ever-increasing cost of land. Another benefit for the underground mine operator is the availability of valuable storage space.

The high cost of transporting crushed stone has dictated that stone be mined and quarried as near as possible to the market centers or manufacturing plants that use it. However, increasing land values and environmental concerns have made it necessary to move crushed stone quarries further away from customers and have driven up the cost of the delivered material for some producers. Overall, however, prices have remained stable since the 1970s, growing just over the rate of inflation due in part to productivity gains and competition.

The average unit value of crushed stone also is expected to increase as a result of rising costs of labor, energy, and processing equipment. In the area of environmental concern, most states are now requiring crushed stone operations to submit environmental impact reports, and many states require a reclamation plan and a use permit application.

The leading states in crushed stone production in the early 2010s were Texas, Missouri, Pennsylvania, Florida, and Georgia. These five states combined to produce 35 percent of domestic production of crushed stone (68.8 million tons). Industry leaders were Vulcan Materials Co., Martin Marietta Materials, and Lehigh Hanson. Vulcan Materials of Birmingham, Alabama, posted revenues of $2.7 billion in 2009. As of January 1, 2010, Vulcan employed 8,227 workers. Raleigh, North Carolina-based Martin Marietta had 2009 sales of $1.7 billion and employed about 4,454 as of January 1, 2010. The company's Martin Marietta Aggregates division, which ran 274 quarries in 27 states, accounted for 90 percent of sales. Lehigh Hanson of Irving, Texas, reported $2.1 billion in sales in 2008 with 14,920 employees. Lehigh Hanson had 129 quarries in 17 states in the late 2000s.

Among market economy countries, the United States is far and away the largest producer of crushed and broken stone. Major international producers include Australia, Canada, Germany, France, Japan, and the United Kingdom. Because of high transportation costs, the international crushed stone trade remains quite minor. Approximately 80 percent of the tiny U.S. crushed stone import market is held by Canada and Mexico.