Natural Aggregates - Foundation of America's Future

crushed stone and sand and gravel, are among the most abundant natural resources and a major basic raw material used by construction, agriculture, and industries employing complex chemical and metallurgical processes. Despite the low value of the basic products, natural aggregates are a major contributor to and an indicator of the economic well-being of the Nation. Aggregates have an amazing variety of uses. Imagine our lives without roads, bridges, streets, bricks, concrete, wall-board, and roofing tiles or without paint, glass, plastics, and medicine. Every small town or big city and every road connecting them were built and are maintained with aggregates. More than 90 percent of asphalt pavements and 80 percent of concrete are aggregates. Paint, paper, plastics, and glass also require sand, gravel, or crushed stone as a constituent. When ground into powder, limestone is used as an important mineral supplement in agriculture, medicine, and household products. Aggregates are also being used more and more to protect our environment. Soil erosion-control programs, water purification, and reduction of sulfur dioxide emissions generated by electric powerplants are just a few examples of such uses. One way to understand and appreciate better the importance of the aggregates industries is to look at their production in the context of all mining. On the basis of either weight or volume, aggregates accounted for more than two-thirds of about 3.3 billion metric tons of nonfuel minerals produced in the United States in 1996. When coal mining is included, the amount of crushed stone and sand and gravel produced still accounts for more than one-half of the volume of all mining and more than twice the amount of coal produced. In this century, the production of aggregates increased from a modest total of about 58 million tons in 1900, when the collection of production statistics began, annual production of crushed stone and construction sand and gravel was the highest ever recorded in the United States for these mineral commodities. It is important to note that of the total natural aggregates produced in this century, more than one-half was produced and consumed in the last 25 years. Of the crushed stone produced in the United States, limestone and dolomite account for 71 percent; granite 15 percent ; and gabbro, basalt, and diabase, also known as traprock, 8 percent. The remaining 6 percent of the crushed stone produced comprises sandstone, quartzite, marble, calcareous marl, slate, shell, and volcanic …