Mineral Facts and Problems: 1960 Edition Page: 78
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MINERAL FACTS AND PROBLEMS, ANNIVERSARY EDITION
try is operated and controlled by the State; in
other countries production is in the hands of
The one large producer in the United States
operates near Hyde Park, Vt., in what is re-
garded as a southern extension of the Quebec
deposits. Approximately a dozen operators
have small chrysotile mines in an area about
60 miles long and 25 miles wide in the Salt
River and Cherry Creek basins of Gila County,
north of Globe, Ariz. These are the only
sources of chrysotile asbestos that have been
developed in the United States, and the small
domestic production reflects the lack of known
deposits having commercial potential. Chryso-
tile deposits are known in California, Montana,
Wyoming, and some other States, but produc-
tion has been negligible. In addition, amphi-
bole asbestos, which has limited use, is produced
sporadically by a few operators in North
Carolina and Georgia.
The largest known asbestos deposits in the
world are in an area 70 miles long by 5 or 6
miles wide between Danville and East Brough-
ton in the Province of Quebec, Canada. Seven
companies are actively engaged in mining in
this area. Five of these are subsidiaries of
companies that operate large asbestos-products
plants in the United States. Several other
companies are prospective producers. In 1950,
one of the companies began operation of a mine
and mill in Munro Township, 12 miles east of
Matheson, Ontario. A new mine began produc-
tion in British Columbia in 1953. Canadian
production in 1958 was valued at more than $95
million, whereas U.S. production had a sales
value of about $5 million.
The Soviet deposits, situated in the Bajenova
district of the Urals, are extensive. The mines
and mills are large, and most of the fiber is
used within the country in the manufacture of
various asbestos products.
Southern Rhodesia is an important producer
of chrysotile asbestos, particularly in the Sha-
bani area. The fiber from these deposits has
such a low iron content that it can be made into
the excellent electrical insulating material that
is required in the construction of electric cables
for use on shipboard. Most of the other de-
posits of the world, except the comparatively
small ones in Arizona and the recently discov-'
ered large one in British Columbia, have a con-
siderably higher iron content, making them
unsuitable for electrical insulation. Swaziland
and the Union of South Africa also produce
chrysotile in substantial quantities. The Union
also produces two special types of asbestos-
amosite, found commercially nowhere else in
the world, and crocidolite (blue asbestos), pro-
duced also in Australia and Bolivia. Most of
the African production is exported (15).
Smaller operations are located in Cyprus,
Italy, Finland, France, Australia, Bolivia,
Brazil, and several other countries.
DEFINITION OF TERMS, GRADES, AND
Asbestos is a name applied to a group of
naturally fibrous minerals. The principal vari-
ety is chrysotile, a hydrous magnesium silicate
having the chemical composition 3MgO . 2SiO2-
. 2HO. Other commercial varieties are amosite,
a complex iron-magnesium hydrous silicate, and
crocidolite, a sodium-iron hydrous silicate. Of
minor importance are tremolite (2CaO . 5MgO-
S8Si02.H20), and anthophyllite (7MgO-
S8SiO2 H20). Asbestos is unique in the min-
eral kingdom because its longer fibers can be
spun into yarn and woven into unburnable
cloth that has many important industrial ap-
plications. The shorter fibers have a multitude
of uses including heat insulation, fireproofing,
brake linings, and building materials.
Chrysotile, the principal variety of com-
merce, is graded according to fiber length.
Fibers three-eighths of an inch long or longer
are classed as the spinning grades suitable for
use in making fabrics. According to the Cana-
dian classification, the crudes (hand-cobbed
long fibers) and spinning fibers comprise
Groups 1, 2, and 3. The succeeding groups are
of progressively shorter fibers. Group 4 is des-
ignated as shingle stock; Group 5, paper stock;
Group 6, waste stucco and plaster; and Group
7, refuse or shorts. Most of these groups are
divided into several subgroups. Such group-
ings comprise the commercial specifications.
The consumer designates the grade desired,
such as 3R or 4K. Grades may be blended to
satisfy special needs. For some uses the chemi-
cal composition is important. Thus, for elec-
tric insulation an upper limit for the iron
content may be specified. The methods of clas-
sification used in the principal producing coun-
tries are discussed in detail in a Bureau of
Mines publication (3).
Most of the chrysotile asbestos deposits of
the world, including those of Vermont in the
United States, Canada, Southern Rhodesia,
Swaziland, the Union of South Africa, and the
U.S.S.R., consist of irregular cross-fiber veins
(closely packed fiber set at a right angle to the
faces of the rock fractures) or slip-fiber zones
(shear planes in rock filled with fiber matted
together parallel to the seam) in massive ser-
pentine. Such deposits commonly extend to
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United States. Bureau of Mines. Mineral Facts and Problems: 1960 Edition, report, 1960; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc38790/m1/86/: accessed April 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.