Environmental Engineering Reference
In-Depth Information
controlled products of the past. Given the widespread use of asbestos minerals prior to the
1970s, poor past working conditions, and a long latency period, new cases of asbestos-related
disease will probably continue to be observed. It will take many more years before the health
benei ts from banning of amphiboles and friable asbestos products which began in the 1970s,
and the regulations which now impose strict factory controls will have a marked effect.
Asbestos materials are still widely used. Modern asbestos products, however, are differ-
ent from the asbestos products used until the 1970s. Old asbestos products, principally low-
density insulation materials, were very dusty and crumbled under hand pressure. Unlike
today's products, they often contained amphibole i bre.
Today, only one type of asbestos is used: chrysotile. In addition, the industry now only
markets dense and non-friable materials in which the chrysotile i bre is encapsulated in a
matrix of either cement or resin. These modern products include chrysotile-cement build-
ing materials, friction materials, gaskets and certain plastics. Ninety percent of the world
production of chrysotile, however, is used in the manufacture of chrysotile-cement, in the
form of pipes, sheets and shingles.
Asbestos minerals of course represent only a minute fraction of all known 3,000 mineral
species (Weiss 1985; Eby 2004), of which only 50 are rock forming (
Table 11.2
).
TABLE 11.2
Common Ore Types (Weiss 1985)
Metal
Ore Mineral
Composition
Percent Metal
Gold
Native gold
Calaverite
Sylvanite
Au
AuTe
2
(Au,Ag)Te
2
)
100
39
Silver
Native silver
Argentite
Cerangyrite
Ag
Ag
2
S
AgCl
100
87
75
Iron
Manganiteti
Hermatite
Limonite
Siderite
FeOFe
2
O
3
Fe
2
O
3
Fe
2
O
3
H
2
O
FeCo
3
72
70
60
48
Copper
Native copper
Bornite
Brochantite
Chalcocite
Cholcopyrite
Covelite
Cuprite
Enarngite
Malchite
Azurite
Chrysocolla
Cu
Cu
5
FeS
4
CuSO
4
3Cu(OH)
2
Cu
2
S
CuFeS
2
CuS
Cu
2
O
3Cu
2
S As
2
S
2
CuCO
3
Cu(OH)
2
2CuCo
3
2H2O
CuSiO
3
2H
2
O
100
63
62
80
34
66
89
48
57
55
36
Lead
Galena
Cerussite
Angiesite
PbS
PbCO
3
PbSO
4
86
77
68
Zinc
Sphalerite
Smithsonite
Calamine
Zincte
ZnS
ZnCO
3
H
2
Zn
2
SiO
5
ZnO
67
52
54
80
(Continued)
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