Minerals Information
The demand for crushed stone is determined mostly by the level of construction activity, and, therefore, the demand for construction materials. U.S. production of crushed stone recorded a significant growth in the past 40 years, from 229 million metric tons in 1950 to 1.1 billion metric tons in 1990. The highest level of production was reached in 1988--1.13 billion metric tons. Between 1950 and 1973, because of the construction of the Interstate Highway System, the growth from year to year in the production of crushed stone was almost continuous, paralleling the increased demand for construction aggregates. Following the reduction in the volume of work in the Interstate Highway Program in the late 1960's, the crushed stone industry, while still growing, became more sensitive to the ups and downs of the economy. The 1974-75 and 1982 recessions are well reflected by low levels of production of crushed stone in those years. Future demand for crushed stone will continue to be dependent mostly on the growth of construction activity.
Most crushed stone is used for construction purposes, mainly as aggregate with or without a binder. Road base or road surfacing material, macadam, riprap, and railroad ballast are the major uses without a binder. Aggregate for cement and bituminous concrete in highway and road construction and repair and in residential and nonresidential construction are the major uses for aggregates with a binder. Other uses include cement and lime manufacture, agriculture, metallurgical flux, and fillers and extenders.
Crushed stone is a high-volume, low-value commodity. The industry is highly competitive and is characterized by thousands of operations serving local or regional markets. Production costs are determined mainly by the cost of labor, equipment, energy, and water, in addition to the costs of compliance with environmental and safety regulations. These costs vary depending on geographic location, the nature of the deposit, and the number and type of products produced. Despite having one of the lowest average-per- ton values of all mineral commodities, the constant dollar price of crushed stone has changed relatively little during the past 20 years. As a result of rising costs of labor, energy, and mining and processing equipment, the average unit price of crushed stone increased from $1.58 per metric ton, f.o.b. plant, in 1970 to $4.39 in 1990. However, the unit price in constant 1982 dollars fluctuated between $3.48 and $3.91 per metric ton for the same period. Increased productivity achieved through increased use of automation and more efficient equipment was mainly responsible for maintaining the prices at this level.
Underground operations are becoming more common, especially for limestone mining in the central and eastern parts of the United States, as the advantages of such operations are increasingly recognized by the producers. By operating underground, a variety of problems usually connected with surface mining such as environmental impacts and community acceptance are significantly reduced.
Transportation is a major factor in the delivered price of crushed stone. The cost of moving crushed stone from the plant to the market often equals or exceeds the sale price of the product at the plant. Because of the high cost of transportation and the large quantities of bulk material that have to be shipped, crushed stone is usually marketed locally. The high cost of transportation is responsible for the wide dispersion of quarries around the country, usually located near highly populated areas. However, increasing land values combined with local environmental concerns are moving crushed stone quarries farther from the end-use locations, increasing the price of delivered material. Economies of scale, which might be realized if fewer, larger operations served larger marketing areas, would probably not offset the increased transportation costs.
Although crushed stone resources are widespread and in adequate supply nationally, local shortages exist. Land use conflicts and environmental problems associated with rapid urban expansion are major factors contributing to these shortages. The local shortages that occasionally exist are caused less by a lack of stone than by urban encroachment or zoning regulations that force closure of operating quarries or prevent the development of new ones. Demand pressures, land use regulations, and the cost of meeting environmental and reclamation requirements are factors that will cause a rising price trend.
Sand and gravel and to a lesser extent iron-blast-furnace slag are the predominant substitutes for crushed stone used as construction aggregate. Steel slag is another substitute for crushed stone in road bases and asphaltic concrete, but not in cement concretes because of chemical interaction. Blast-furnace slag is also used as a stone substitute in cement manufacturing.
Stone remains an abundant material, and, despite environmental, zoning, and regulatory restrictions, no shortages on a large scale are expected to occur in the future.