70 



UNITED STATES MINERAL RESOURCES 



Eastern Townships, and this established district 

 contains at least three-quarters of identified Cana- 

 dian reserves. Much of the terrane encompassing 

 the more recently exploited deposits is yet to be 

 evaluated geologically. Pending determination that 

 the later developed asbestos-bearing areas are as 

 consistently geologically favorable as the Eastern 

 Tovi^nships belt, the latter must continue to be re- 

 garded as the most promising area in the Americas 

 for undiscovered resources. 



The first deposit opened in northern Ontario v^^as 

 depleted within 15 years, but other deposits in the 

 general vicinity are taking its place, and continuing 

 exploration provides promise for additional exploit- 

 able resources in that area. The Precambrian ter- 

 rane that is host to these occurrences is structurally 

 complex and commonly poorly exposed, and the po- 

 tential asbestos deposits require rigorous geologic 

 study and extensive drilling programs for evalua- 

 tion. None of the Ontario occurrences have yet been 

 shown to have the potential of the larger deposits 

 of the Eastern Townships belt. 



Occurrences elsewhere in eastern Canada do show 

 promise of sustaining large-scale operations. Sig- 

 nificant reserves have been outlined in Maizerets 

 Township and near Chibougamau, respectively about 

 300 miles northwest and north of Ottawa, and in a 

 third deposit 800 miles farther north on the Un- 

 gava Peninsula. If viable mining operations ma- 

 terialize in these three widely separated localities 

 in Quebec, they may well give the impetus to search 

 out additional large resources in the Precambrian 

 ultramfic terrane of the province. 



Soon after mining of the Advocate deposit, on the 

 north coast of Newfoundland, began in 1963, a 

 yield in excess of 60,000 tons of fiber annually was 

 established. With expansion of facilities, production 

 of 100,000 tons annually is anticipated. The success 

 of the Advocate development may spark continued 

 prospecting of the many ultramfic bodies of New- 

 foundland. 



The discovery in 1950 of the Cassiar deposit on 

 McDame Mountain in northern British Columbia, 

 and subsequent rapid implementation of the mining 

 operation — which started in 1953 despite problems 

 such as rigorous climate, permafrost, and transpor- 

 tation logistics related to remote location — stimu- 

 lated search for other deposits in the northern part 

 of the Pacific Coast ultramafic belt. The Cassiar 

 reserve, of some 25 million tons of ore with a con- 

 tent of 8-10 percent asbestos that mills free of 

 magnetite and includes a high proportion of long 

 fibers, has eliminated long-standing dependence on 

 Rhodesia for strategic low-iron textile fibers. Com- 



parable reserves were ultimately outlined at the 

 Clinton Creek deposit, 65 miles northwest of Daw- 

 son City in the Yukon Territory and within 9 miles 

 of the Alaskan border, and mining started in 1968. 

 The Cassiar and Clinton Creek mines furnished 

 more than 10 percent of Canadian production in 

 1969-70. West-northwest of the Clinton Creek de- 

 posit and as much as 80 miles into Alaska a few 

 occurrences of chrysotile have been reported (Fos- 

 ter, 1969). That part of the ultramafic belt that 

 extends through interior British Columbia, across 

 Yukon Territory and perhaps 150 miles or more into 

 the Yukon-Tanana upland of east-central Alaska is 

 a prime target for much geophysical and geologic 

 e^'aluation. 



UNITED STATES 



Prior to the early 1960's, about 80 percent of the 

 asbestos produced in the United States had been 

 mined from deposits on Belvidere Mountain, near 

 Lowell in northern Vermont. Currently about 

 40,000 tons of medium- to short-length chrysotile 

 fibers are produced annually from those deposits. 

 Reported reserves are more than 1 million tons of 

 fiber. This remains the only locality in the Appa- 

 lachian belt within the United States where minable 

 concentrations of chrysotile asbestos are known or 

 are likely to be found. Along the southern part of 

 of the belt, particularly in western North Carolina 

 (Conrad and others, 1963) and northeastern Geor- 

 gia (Bowles, 1955, p. 25-26), many small deposits 

 contain in aggregate an anthophyllite resource of 

 more than 100,000 tons. 



Although the ultramafic rocks of California have 

 been much prospected and intermittently yielded 

 small quantities of asbestos after 1882, no mining 

 operation of large scale was developed until 1962, 

 when a plant with a capacity of 2,500 tons of ore 

 per day began operation on a deposit near Copper- 

 opolis in Calaveras County. The unusual short- 

 fiber deposits in eastern San Benito County and 

 western Fresno County, northwest of Coalinga, also 

 were first exploited in 1963. California immediately 

 became the principal asbestos-producing State and 

 currently furnishes more than 75,000 tons of chryso- 

 tile fibers annually. 



The host for the occurrences near Coalinga is an 

 intensely sheared mass of serpentinite 14 miles long 

 and 4 miles wide. The chrysotile occurs as fibers 

 largely indiscernible to the eye that are matted in 

 leathery flakes along closely spaced shear planes. 

 Chrysotile occurs extensively in this form in the 

 southeastern half of the serpentinite mass. Fiber 

 content is highly variable, but locally exceeds 50 



