Mining Methods Vary Widely - Mining and the Environment: From Ore to Metal - page 224

FIGURE 5.1
Metals and Industrial Materials
Consumed in the USA, 1900 to 1995

Recession

Metric
Tons
(millions)

300

Oil Crisis

Economic
Expansion

Construction materials (crushed
stone, sand and gravel) are separated
from the remainder of the industrial
minerals to illustrate the upsurge in
construction following the end of
World War II.
Source:
David McConnell 1998-2001

200

World
War II

Great
Depression World

War I

100

0

1900 1925 1950 1975 1995

Construction Materials
Industrial Materials

Metals

Dimension stone refers to rock that is cut to a certain shape and size, commonly used as
building material: limestone, granite, dolomite, sandstone, marble, and slate ( Case 5.3 ).
Processing the stone begins with sawing the excavated rock into slabs using a rotating diamond
or circular saw. Water is used to cool the saws and to remove particles. After the stone has been
cut to the desired size, it is i nished using natural and synthetic abrasives. Natural abrasives
include iron oxide, silica, garnet, and diamond dust, themselves usually products of mining.
Synthetic abrasives include silicon carbide, boron carbide, and fused alumina (USEPA 1995).
Nearly all the principal types of stone, including granite, limestone, sandstone, dolomite,
and marble may be used as sources of commercial crushed and broken stone or aggre-
gate . Stone that breaks in chunky, cubical fragments and is free of surface alteration from
weathering is preferred for crushed stone. Most crushed and broken stone is mined from
open quarries. Processing activities include blasting, conveying, screening, secondary and

Most crushed and broken stone
is mined from open quarries.

CASE 5.3
Mining Carrara Marble

The Carrara marble quarries have been in operation for
more than 2,000 years. Carrara marble, found in northern
Tuscany, is famous for its statuary quality and it has been
used by the most famous sculptors including Michelangelo,
Donatello, Jacopo Della Quercia and Canova. The name of
Carrara, Tuscany became synonymous with marble. Carrera
marble continues to be requested worldwide for buildings,
statues, and other ornamental objects, and about one
million tons of marble is quarried each year.