Document xzBmkY1xXEx43pQq9Q1M0LDyb

' " Jl! , 1* u -^Ur^-Ssk' *!> U\* -.<-;v.' -'v'r' * UNITED STATES DEPARTMENT OF THE INTERIOR -1959 /i - /: A^7 *%X- 'jS? * , U '.* .* ' '.^V* *>: I, 'i. * *. I ASBESTOS A Materials survey By Oliver Bowles ***************** Information Circular 7880 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959 _ - UNITED STATES DEPARTMENT OF THE INTERIOR Fred A. Seaton, Secretary BUREAU OF MINES Marling I. Ankeny, Director The Library of Congress has cataloged this publication as follows: Bowles, Oliver, 1877-195S. Asbestos, a nv.iterials survey. tRev.j Washington, U. S. Govt. Print. OH'., 1959. ix, 94 p. illus., maps. 27 cm. (tU. So Bureau of Mines. Infor mation circular 7S80) First ed. compiled by the U. S. Bureau of Mines and published in 1952 under title: Materials survey, asbestos, 1950. Includes bibliographies. 1. Asbestos. asbestos, 1050. i. U. S. Bureau of Mines. Materials survey, (Series) TN295.U4 no. 78S0 338.2707 58-60080 Library of Congress For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price $1.25 (paper) OFFICE OF THE DIRECTOR UNITED STATES DEPARTMENT OF THE INTERIOR BUREAU OF MINES WASHINGTON 25, D. C. September 15, 1958 Hon. Leo A. Hoegh Director Office of Civil and Defense Mobilization Washington 25, D. C. . Dear Mr. Hoegh: The Materials Survey on Asbestos, originally published in February 1952, under an agreement with the National Security Resources Board, has been revised. Copies are being forwarded to you. This is the first Materials Survey to be revised under the terms of the April 15, 1955, agreement between the Departmentof the Interior and the Office of Defense Mobilization, which as signed responsibility to Interior for preparation and revision of Surveys covering 45 mineral commodities. Manuscript revisions proposed by reviewing officials of the Office of Civil and Defense Mobilization have been incorporated in the Survey. Sincerely yours, ACTING Director in Foreword Materials Surveys are designed to bring into a single document all the fundamental data needed by war or defense personnel with major responsi bilities with respect to Survey subjects. The Surveys dealing with metals and minerals summarize the demand-supply position in the United States and* include information on production, imports, consumption, exports, capacity, interchangeability, substitutes, possibilities for expansion, ana pertinent his-, tory, usually in some detail back to 1935. The properties of the commodity are described. Exploration', mining, milling, and processing methods and domestic and foreign resources and reserves are discussed. An extended pres entation of the structure of the industry covering major corporations, trans portation service, processing facilities, interrelationship to other industries, fjertinent laws ana taxation policies, tariffs, Government controls, special abor problems, and history of wartime control experiences is included. Other special data are presented for particular commodities. The first edition of Materials Survey--Asbestos, prepared by the Bureau of Mines, was published in February 1952. The present report, prepared in the Division of Minerals under the direct supervision of G. W. Josephson, Chief, Branch of Construction and Chemical Materials, is a revision of the earlier Survey, made in accordance with the agreement between the Office of De fense Mobilization and the Department of the Interior dated April 15,1955, that revisions of the Surveys should be made periodically. Sucli revisions are essential because conditions governing production and consumption are con stantly changing. New deposits may be discovered and exploited while other deposits may be depleted. Changing economic factors may curtail production in certain areas and expand it in others. Thus, production patterns may shift, the emphasis varying from point to point, from country to country, and even from continent to continent. Similarly, in the field of utilization, substitution of alternate materials for a mineral commodity may increase; on the other hand, new and wider uses for the mineral may be developed. New equipment designs or new proc esses may increase or diminish the quantities of the mineral needed for specific uses. Changes in specifications or results of research may contribute to modifi cations in the use pattern. Copies of the original Asbestos Survey were sent to many competent reviewers with a request for comments or corrections. Numerous respondents in the United States and in several foreign countries furnished supplemental or corrective data that have been incorporated in the revision. The revised manuscript was reviewed in whole or in part by specialists in the Bureau of Mines, the Geological Survey, the Department of Defense, and industry. Grateful acknowledgment is made to the reviewers of boLli the original and the revised report for their cordial and constructive response. Ciiauuss W. Mehiuu,, Chief, Division of Minerals. v CONTENTS Foreword Summary and introduction____________________ Essentiality of asbestos........................... ......... Shortage of domestic supplies.................. Upward trend of both world demand and supply...... ......................................................... Adequate information an imperative need___ Chapter 1. Varieties and composition of asbestos Varieties Chrysotile asbestos_______________________ Amphibole asbestos______________________ Amosite Anthophyllite......... ,......... ................... ....... Tremolite.........*.......................................... Crocidolite.......... ......................... ............... Erratic character of amphibole fibers____ Importance of physical properties___________ Bibliography-------------------------------- --------------Chapter 2. Description of deposits___________ Domestic deposits__________________________ Vermont Arizona Other occurrences________________________ Foreign deposits____________________________ Canada Suebec ntario British Columbia______________________ Newfoundland_________________________ Southern Rhodesia_____ _________________ Union of South Africa____________________ Cape Province________________________ Transvaal Natal.................... Swaziland 10 U. S. S. R......................................................... Venezuela-_______________________________ Bolivia 10 Greece 11 Italy............................................... Australia 11 New Zealand____ ________ China 11 Japan................... Finland................................. .......... ............... Cyprus..________________________________ Inaia_______ Morocco..__________ Other countries 12 Bibliography............................... Chapter 3. Exploration....................... Current progress in exploratory work________ Methods and problems of exploration............. Essential requirements of new discoveries----- Chapter 4. Mining methods........................... Arizona........................................................ Vermont______ ____________________________ Canada............................... Southern Rhodesia_____ ___________________ Union of South Africa________ Swaziland...______ _____ U. S. S. R............................................................. Other countries.._________ Bibliography..................................... Chapter 5. Klilling methods-------------Definitions.......................... ........... ..... .'.---------General features................................... Face v 1 1 2 2 2 3 3 3 3 3 4 4 4 4 4 5 6 6 6 6 7 7 7 7 8 8 8 8 9 9 9 10 10 10 11 11 11 11 11 11 12 12 13 13 13 14 15 15 15 15 10 10 10 10 17 17 18 18 18 Chapter 5--Continued Canada___ --------------------- ---------------------------Capacity------------------------ ------------------------Arizona................................................. ............... Vermont...................... ------------------------------Union of South Africa........................................ Southern Rhodesia Swaziland...... ......... ............... -................... ....... U. S. S. R.......................................................... Supplementary milling in asbestos textile factoriesf_____________ ___________ Bibliography...................................... ................. Chapter 6. Grading and classification------------ Canada British Columbia Arizona Vermont------------------------------ ----------------------Union of South Africa----- ---------------------------- Crocidolite------------------------------- --------------Amosite---- ----------- ---------------------------------Chrysotile..------- ------------------------------------ Southern Rhodesia Chrysotile Swaziland----- ---------------------------------------------Chrysotile U. S. S. R............................................................. Chrysotile....................................................... India...................................................................... Chrysotile..... ......................................... .......... Stockpile grades and specifications---------------Chrysotile..... ..................................... ............. Amosite Crocidolite Chapter 7. World production and consump tion.............................................................. -- World output...................................................... Output, by countries.......................................... United States........................ ......................... Canada.............................................. ............... Union of South Africa Southern Rhodesia....................................... U. S. S. R......................................................... World consumption........................ ............... .. Bibliography.................................... --............. Chapter 8. World reserves............ ........... ......... Importance of reserves_____________________ United States------------ --------------------------------Canada U. S. S. R.......................-.................................... , Southern Rhodesia.................. ........................... Union of South Africa Transvaal..................................... ---------------Cape of Good Hopes....... ........... ................... Swaziland----- --------------------- -----------------------China................................ ------------ ---------------Australia....... .................................................... World estimate...................................... ............. Summary........................................ -................... Bibliography........................................................ Chapter 9. Political and commercial control-- Significance of industry control........................ Political control............................ ............. ........ Commercial control----------------- -------------------- Chapter 10. International trade_____________ Extent of international trade Foreign trade of the United States..... ........... Consumption.................................................... Imports................... ........................................ VII Face 18 19 20 20 21 21 22 22 22 23 24 24 25 25 25 25 25 25 26 26 26 26 26 26 26 26 26 26 26 27 27 28 28 28 28 28 31 31 32 32 32 33 33 33 33 34 34 34 34 35 35 35 35 35 35 35 30 30 30 30 37 37 37 37 37 VIII ASBESTOS--A MATERIALS SURVEY Chapter 10--Continued Foreign trade of the United States--Con. Chapter 18--Continued World War II controls and experiences--Con. Exports____________________ Export control------ -----------Foreign trade of Canada--................. Foreign trade of Southern Rhodesia................ Foreign trade of the Union of South Africa 40 40 41 43 War Production Board Conservation Order M-79, as of September 30, 1942............ War Production Board Conservation Order M-123 as Amended December 14, 1942--Asbestos Textiles......................... and Swaziland..... ........................................... Chapter 11. Industry structure.......................... General structure......................................... 44 47 47 Restricted Uses of Asbestos Textiles Un der Conservation Order M-123 as Amended December 14, 1942............ Marketing problems..-------------------------------- 47 List A Necessity for a balanced market____________ Sale and' distribution practices.......................... 48 48 List B_______________________ _______ War Production Board Conservation Order Chapter 12. Prices................................................ Price history of Canadian and United States 50 M-283--Asbestos Textiles......................... War Production Board Conservation Order asbestos______________________ 50 M-283 as Amended March 17, 1943-- Prices of African asbestos................................... Chapter 13. Uses and requirements of use___ 51 53 Asbestos Textiles..... ................................... War Production Board Supplementary General features 53 Conservation Order L-41-d--Construc- Spinning fibers 53 Textile uses__________ Nontextile uses of long fibers_____________ 53 54 War Production Board Conservation Order M-79 as Amended October 1, 1943-- Friction materials---------------------- 54 Cork, Asbestos, and Fibrous Glass------ Miscellaneous nontextile uses----- ---------------- 54 Asbestos Interchangeability of grades...... ............ Uses of amosite 55 Uses of crocidolite......... ..................................... Distribution of asbestos according to use------- 55 55 56 War Production Board Conservation Order M-123 Revocation--Asbestos Textiles War Production Board Conservation Order M-79 as Amended January 31, 1944-- Directory of asbestos products manufacturers. 57 Cork, Asbestos, and Fibrous Glass____ Fabrication of asbestos products...................... 58 Asbestos....................................................... Fabrics......................................... Shingles and lumber---------------- 59 War Production Board Conservation Order 59 M-79 as Amended December 8,1944-- Paper and millboard_____________________ 60 Cork, Asbestos, and Fibrous Gloss___ Asbestos-cement pipe------------ 60 Asbestos........................................................ Asbestos-magnesia insulation............. 60 War Production Board Conservation Order High-temperature insulation______________ 60 M-283 as Amended January 4, 1945-- Compounded packings........................ '61 Cork, Asbestos, and Fibrous Glass___ Asbestos cement.................. Molded articles...---------------Noncorrosive filters________ 61 Asbestos Textiles................. ....................... 61 Restricted Uses of Asbestos Textiles Un 61 der Conservation Order M-283 as Bibliography....................................... 61 Amended October 11, 1943 Chapter 14. Substitutes for asbestos_________ 62 List A................ ................................. -- Incentives for substitute research..................... 62 List B_______________________ _______ Soda-lime-silica glass fibers and mineral wool. 62 War Production Board Conservation Order High-silica glass fibers..................................... 63 M-79 as Amended March 20, 1945-- Other siliceous fibers......................................... 64 Cork, Asbestos, and Fibrous Glass___ Organic substitutes__________________________ 64 Asbpstos.................. ..................... ............... Substitutes for amosite....................................... 64 War Production Board Conservation Order Substitutes for crocidolite..................... 64 L-41-d, Revocation--Construction......... Bibliography........................................... 65 War Production Board Conservation Order Chapter 15. Beneficiation of asbestos_________ 66 M-283 as Amended August 11, 1945-- The low-iron problem...................................... 66 Cork, Asbestos, and Fibrous Glass___ Treatment of high-iron asbestos..... .......... 66 Asbestos Textiles...................................... Elongation of short fibers............................... 67 Restricted Uses of Asbestos Textiles Un Bibliography............................................. 68 der Conservation Order M-283 as Chapter 16. Asbestos synthesis______________ Synthesis of chrysolite....................... Synthesis of amphiboles.................... Synthesis of asbestiformproducts..................... Bibliography............................................................. Chapter 17. Government Stockpile program. Chapter 18. War controls and experiences____ World War II controls and experiences.. . . Office of Production Management Conser vation Order M-79 Curtailing the Use of Certain Types of Asbestos.............. War Production Board Conservation Order M-79 Curtailing the Use of Certain Types of Asbestos, Amendment 1............... War Production Board Conservation Order M-123--Asbestos Textiles............................. 6!) 69 69 71 71 73 75 75 76 77 77 Amended August 11, 1945............... List A...................................................... List B...................................................... ,, War Production Board Priorities Regula tion 31 as Amended August 1945-- Regulations Applicable to the Opera tion of the Priorities System Blanket Revocation of Certain WPB Orders................................................... Building Materials.................................. Cork, Asbestos, and Fibrous Glass____ Paper.................................................. ...... War Production Board Conservation Orders M-79, Asbestos, and M-283, Asbestos Textiles, Revocation Post World War II Controls.......................... National Production Authority Order War Production Board Conservation Order M-96--Spinning Grades of Chrysolite M-79 ns Amended June 18, 1942--As Asbestos Fiber.................................... .. bestos............................................................... 78 Schedule A of XPA Order M-96............. War Production Board Conservation Order National Production Authority Order M-123 as Amended July 4, 1942--As M-96, Revocation--Spinning Grades of bestos Textiles..................................... 79 Chrysotile Asbestos Fiber.......................... Page 79 80 81 81 82 82 83 84 85 85 86 86 86 87 87 87 87 89 89 89 89 89 90 90 90 92 92 92 92 92 92 92 92 92 93 93 94 94 I ( CONTENTS ILLUSTRATIONS IX Fig. 1. Map of major world asbestos deposits____________ ________________ ______ -..................................... ......... 2. Map of Quebec asbestos region.................................... ........................................................................................ 3. The largest asbestos mill in the world, Canadian Johns-Manville Corp. mill, Asbestos, Quebec------------- 4. Mill of Vermont Asbestos Mines, near Eden, Vt______________________ _____ ........................................-- 5. Map showing world production of asbestos and production, by countries......... ...................... 6. Asbestos exports ana imports, by countries, 1949, 1951, and 1953---7. Average yearly price of Canadian asbestos per ton, 1929-56______________________________ 8. Synthetic amphibole asbestos--------------------------- 6 8 20 21 28 38 51 71 TABLES 1. Sales of asbestos in Arizona, 1914-45________________________________________________________________ 2. Canadian milling capacity, 1956....________________________________________ ________________________ 3. World production of asbestos, by countries, 1947-51 (average) and 1952-56---------------------------------------4. Asbestos sold or used by producers in the United States, 1925-56----- -------------------------------------------------5. Production (shipments) of asbestos in Canada, 1935-56, in short tons.............................................. ........... 6. Production (shipments) of asbestos in Canada, by grades, 1950-56, in short tons--------------------------------7. Production of asbestos in the Union of South Africa, by kinds, 1935-56, in short tons--------- -------8. Asbestos production in Southern Rhodesia, 1935-56 9. Asbestos production in U. S. S. R 10. Consumption of asbestos, by countries or regions, 1950-55, in short tons--------------------------------------------11. Asbestos reserves of chief producing countries, thousand snort tons............................................................ 12. Apparent consumption of asbestos in the United States, 1935-56........... ........... ........................................... 13. Imports of asbestos into the United States, by principal countries of origin, 1935-56, in short tons------14. Imports of spinning grades of asbestos into the United States from Canada, 1945-56, in short tons.... 15. Total shipments and imports into the United States of Canadian crudes and spinning fibers, 1949-56, in short tons................................... ............................................................... ........................................................... 16. Asbestos (chrysotile) imported for consumption in the United States from Southern Rhodesia, by grades, 1943-56, in short tons_______________________________________________________ _____________________ 17. Imports of amosite and crocidolite (blue asbestos) into the United States, 1943-56, in short tons--------- 18. Exports of asbestos from the United States, 1947-56.........--......................................................... ............... 19. Exports of asbestos from Canada, by country of destination, 1935-55, in short tons................................... 20. Exports of asbestos from Southern Rhodesia, by principal countries of destination, 1935-56, in short tons. 21. Exports of asbestos from the Union of South Africa and Swaziland, by principal countries of destination, 1935-55, in short tons.......................................... ............................................................................................... 22. Exports of chrysotile from the Union of South Africa, by principal countries of destination, 1945-56, in short tons______________________________________________________________________ _________________ 23. Exports of amosite from the Union of South Africa, by principal countries of destination, 1945-56, in short tons....................... ............... ............................................................................................... ..................... 24. Exports of crocidolite from the Union of South Africa, by principal countries of destination, 1945-56, in short tons............... ............... ..................... ..................... ........................................... ..................................-- 25. Price history of asbestos sold in Canada, in dollars per short ton, 1926-56________________ _____ _ 26. Prices of Vermont asbestos, in dollars per short ton, 1931-56.... ........................... -............................... ....... 27. Prices of Arizona asbestos, in dollars per short ton, 1952-56........ ................................... ......................... -- 28. Approximate prices of Rhodesian asbestos, in dollars per short ton, 1946-56....................... ....................... 29. Asbestos content and heat resistance of asbestos fabrics..----------------------------------- -----------------------------30. Allocation of strategic grades of asbestos in 1944, by end use, textile uses............................ ............... ....... 31. Allocation of strategic grades of asbestos in 1944, by end use, nontextilu uses...... ............... S............ ........ 32. Correlation of allocation and actual use of strategic grades of asbestos during 1944---------------- ------------- 33. Allocation of asbestos, by end use, in 1944.......... ..................................................................... ........... ......... 34. Value of shipments of asbestos products in the United States, 1954-55........................................................ 35. Value of asbestos products exported from the United States, 1951-56------------------------------- ----------- -----36. Cell dimensions of natural and artificial tremolite 6 20 28 30 30 31 31 32 32 32 35 37 38 39 39 39 40 40 41 43 44 45 45 46 50 51 51 52 53 56 57 57 57 58 58 70 i i ASBESTOS' *- A MATERIALS SURVEY BY Oliver Bowles* Summary and Introduction "Asbestos" is a name applied to a group of naturally fibrous minerals. Because it has the fibrous characteristics of silk or cotton and at the same time will not burn and has other advantageous properties as well, asbestos has specialized uses for which no adequate substitutes are yet available. Asbestos furnishes a major raw material for a great variety of essential prod ucts, the manufacture of which constitutes a vast industry. Asbestos generally occurs in irregular veins scattered throughout rock masses. Most of the fiber-bearing rock is mined in huge open-pit or under ground workings. The fibers are separated from the rock ana sorted into groups, according to length, in large, complex mills. The longer fibers are shipped to textile plants, where they are further fiberized ana prepared in special machines and are used for spinning into yarn and weaving into un fa nrnable cloth that has many important uses. The shorter fibers, which are much more abundant than the long ones, are used in asbestos-cement building materials in heat-insulating products and for a multitude of other applications. These processes and uses are covered in considerable detail in later sections of this report. This report gives primary consideration to the types and grades of asbestos that are of greatest importance in the program of military preparedness-- namely, the spinning grades of chrysotile, both foreign and domestic, and the amosite and crocidolitc obtained only from foreign sources. ESSENTIALITY OF ASBESTOS ^ The United States has developed the greatest asbestos-products industry in the world. The value of such products manufactured in 1953 was $345 million and in 1954, $323 million. These products are not only vital to build ing construction and industry but arc absolutely essential to certain other important fields of use. For example, virtually all brake lining and clutch facings of automobiles, trucks, or other mobile equipment used in peace or war consist essentially of asbestos. Hence, a shortage of asbestos used in friction materials would tend to immobilize highway transport. Also, there is no known substitute for asbestos used in steam packings. Accordingly, a shortage of such products would interfere seriously with many lines of industrial activity. Satisfactory replacements for the amosite variety mined only in South Africa for felted insulation of marine turbines can be obtained only at exorbitant prices. Crocidolitc (blue asbestos), mined in Africa and Australia, is regarded as a necessary constituent of asbestos-cement pipe. 1 Work uii manuscript completed January 1D58. * Former consultant commodity specialist, Bureau of Mines (deceased). ASBESTOS--A MATERIALS SURVEY Many other examples might be cited to indicate the essentiality of asbestos to our modern way of life and to any program of military preparedness. SHORTAGE OF DOMESTIC SUPPLIES This great asbestos-products industry has been built up under conditions of overwhelming dependence upon foreign supplies of raw asbestos. Domestic mines furnish only 6 to 8 percent of our requirements of all grades and an even smaller percentage of the important strategic grades. Canada and Africa are the principal foreign sources. Canada supplies most of the short-fiber demands of the United States and a major part of the longer textile-grade fibers. Africa formerly supplied a low-iron asbestos essential to important military needs where fireproof electrical insulation is involved, but such supplies are now obtained chiefly from British Columbia, Canada. Africa is our only source of the asbestos variety amosite, which is of first importance as light weight insulation on ships and airplanes. Africa is the principal source of crocidolite (blue asbestos), which has certain special uses. Bolivia supplies small quantities and is the only source of crocidolite in the Western Hemisphere. UPWARD TREND OF BOTH WORLD DEMAND AND SUPPLY The asbestos-products industries of the United States are expanding greatly to pace, growing industrial activity; therefore the domestic demand for raw asbestos is increasing steadily. British and continental European needs are also expanding. Central European asbestos-products industries, stagnant during World War II, have revived, and increasing quantities of African and Canadian fibers are being shipped to European markets. Australian demands are also rising substantially. Canadian and African production facilities re cently have been greatly enlarged, and further increases are expected. Supplies of fiber adequate to meet growing world needs appear to be ample for the near future, but the long-term prospect is less definite. ADEQUATE INFORMATION AN IMPERATIVE NEED The procurement of necessary supplies is a problem of worldwide scope, and in every war emergency asbestos assumes top priori13' among strategic minerals. It is of paramount importance, therefore, that a thorough Knowledge should be gained of tire composition and properties of asbestos, its uses and requirements for each use, grades and specifications, the degree of essentiality of each application, the nature and extent of sources of supply throughout the world, mine and mill capacity, reserves, transportation facilities, political and commercial control, world requirements by countries, import and export data, allocation of supplies, fiber bcneficiation, possibilities of synthetic asbestos manufacture, use of substitute materials, past war controls, war history, and various other problems that may appear. The purpose of this report/is to furnish information on ns many as possible of these pertinent questions. CHAPTER 1. VARIETIES AND COMPOSITION OF ASBESTOS VARIETIES There are several varieties of asbestos, differ ing considerably in composition and physical properties. The most important commercially is chrysotile, which constitutes about 95 percent of total world production. Its wide use is due to the fact that its fibers are generally strong and flexible and therefore can be applied to many uses, such as manufacture of textiles and steam packing, for which weak and brittle fibers are -not adapted. Species of asbestos other than chrysotile fall in the amphibole group of minerals. The only varieties having significant use are anthophyllite, tremolite, amosite, and crocidolite. Fibers of anthophyllite and tremolite are generally weak ancl brittle, and their uses are limited. Sales are small,'and only small quantities of these materials enter international trade. Amosite and crocidolite are mainly African varieties exported to the United States and other countries in considerable quantities for specialized uses. CHRYSOTILE ASBESTOS Chrysotile is a hydrous magnesium silicate having a composition represented by the chem ical formula SMgOBSiOs'BHsO. It is a fi brous form of the mineral serpentine. Antigorite is a platy form of serpentine of no com mercial value. In recent work Shaw (5)3 indicates that both Oil, the hydroxyl radical or water of con stitution, and H-O, the water of crystallization, are present in chrysotile. To indicate the dual nature of the water content, he writes the chemical formula (OH)0^Ig0Si4Oi,HsO. He claims also that in fibers from different loca tions the proportions of these two forms in which water occurs may vary. Thus, in Cana dian chrysotile a greater part of the hydration is water of crystallization, while in the Rhode sian chrysotile the hydration is due largely to the hydroxyl radical. He expresses the view that such a difference in chemical constitution may explain in part the superior electrical resistance of the Rhodesian fiber. The composition of chrysotile, however, is not rigidly fixed according to either of the for- 3 I tiillcl/.ed uumbprn In nnrcntliotsra refer to items in tbc blbllocrupliy at tbc cud of this chapter. mulas given above. Minor quantities of iron, nickel, manganese, or aluminum may replace part of the magnesium. Such small replace ments may result in some modifications in the physical properties of the fibers. Furthermore, these properties are influenced to some extent by the presence of impurities; but, in general, chrj-sotile is more constant and dependable in quality than other varieties of asbestoS. Chem ical analyses of representative samples of as bestos are given in Bureau of Mines Bulletin 552 (7). AMPHIBOLE ASBESTOS The amphibole group of minerals was for merly believed to consist of anhydrous silicates of magnesium, calcium, iron, and other ele ments. However, in 1916 Schaller (), using five exact analyses of tremolite, showed, by cal culating the molecular ratios, that water was an integral part of the composition of tremolite and derived the formula 2CaO oMgO SSi02 H20, which is now the recognized composition as contrasted to the widely published formula CaO 3>IgO 4Si02. When X-ray studies of minerals were begun in the early 1920!s, Schallers findings were confirmed, and it was further learned that all amphiboles contained water of crystallization. Only in textbooks of mineralogy published since about 1940 will the definite statement be found: "All amphi boles contain hydroxyl." The water content of amphiboles is low--only 1 or 2 percent-- whereas chrysotile contains about 13 percent water. AMOSITE There is some doubt that amosite is a distinct mineral species. Rabbitt (4) found by X-ray analysis of two amosite samples from South Africa that both were monoclinic in crystal lization and therefore were not anthophyHites. The chemical composition of one indicated that it was probably actinolite, and the other was probably cummingtonite. Vennas (6) con cludes that amosite is a fibrous form of the monoclinic amphibole grunerite (FeMg)7SiH0-2(0II)2. However, it seems desirable to re tain the name amosite in commercial usage where it serves a useful purpose. Amosite may contain as high as 40 percent iron oxide, but, as it is monoclinic in crystal lization it is not a true anthophyllite, although 3 4 ASBESTOS--A MATERIALS SURVEY it is commonly classed as a high-iron anthophyllite. Amosite, unlike the true anthophyl lites, which are almost invariably weak and brittle, consists commonly of long, fairly strong fibers that have certain specialized uses. It is mined only in Africa. ANTHOPHYLLITE The composition of antliophyllite is now gen erally expressed by the formula Mg7(Si4On)2(0II)2, sometimes written 7MgO 8Si0J-I20. The magnesium may be replaced in part by certain other elements, but complete replace ment is not possible because the anthophyllites possess only limited isomorphism. Ferrous iron may replace magnesium up to 26.53 per cent, but. such an antliophyllite would still con tain as much as 11.48 percent MgO. When the ferrous iron content exceeds 26.53 percent, the mineral ceases to be antliophyllite, as it be comes monoclinic in crystallization whereas all anthophyllites are orthorhombic. The MgO content of antliophyllite is said to range from 5 to 50 percent. A series of 46 chemical analyses of anthophyllites assembled by Rabbitt (4) shows a maximum of 31.53 per cent and a minimum of 11.48 percent. The one with the maximum MgO content contained 5.6 percent FeO. The CaO content of anthophyliites is very low; it averages about 0.5 percent and rarely exceeds 2 percent. Aluminum is a more important constituent of anthophyllites than is commonly supposed. Of Rabbitt's 46 tabulated analyses, 14 show more than 10 percent Al2Os, and 20 show more than 5 percent. Aluminum may. replace mag nesium or silicon. TREMOLITE In tremolite the calcium may be replaced in small part by sodium. The magnesium is re placeable by iron in considerable quantities and by aluminum to a lesser degree. Also, a small part of the silicon may be replaced by alumi num. Tremolite usually consists of gray to white sillcj' libers, which arc for the most part weak and brittle, although fibers of consider able strength and flexibility are found at times. Both tremolite and antliophyllite are superior to chrysotilc in resistance to chemical reaction. CROCIDOLUE Crocidolito or blue asbestos belongs to the hornblende group of amphiboles. Its simplest chemical formula is 3Na20-6Fe0-2Fe203,16Si02TI20. Considerable variation in compo sition has been noted. Sodium may be replaced by potash, ferric and ferrous iron by magne sium or manganese, and ferrous iron by alumi num. Mineralogists now regard crocidolite as identical with riebeckite, being merely a fibrous form of that mineral. Crocidolite therefore bears the same relation to riebeckite that amosite bears to grunerite and that chrysotile bears to massive serpentine. Blue asbestos is produced chiefly in South Africa, but substan tial quantities are now obtained in Western Australia, and a small output is obtained in Bolivia. Except for those in Bolivia and a recently discovered occurrence in New Quebec, Canada, no commercial deposits of blue asbes tos are known in the Western Hemisphere. In Bolivian blue a large part of the iron is re placed by magnesium. The magnesium con tent of African blue asbestos is somewhat lower. ERRATIC CHARACTER OF AMPHIBOLE FIBERS As may be observed from the foregoing dis cussion, the replacement of one element by another in varying proportions is a prevalent characteristic of the several varieties of amphi bole asbestos. This variation in composition results in coi'responding changes in their physi cal properties. These properties may also be influenced by the presence of impurities. The somewhat erratic and unpredictable physical characteristics of the amphibole fibers have a profound influence on their use. . An anthophyllite from one locality may give satisfactory service for some specific use, while one from another deposit, although appearing to be exactly the same, may be unsatisfactory. Thus, problems in amphibole asbestos procurement are much more difficult and complex than the procurement of mineral products like iron or copper, which, when pure, have constant prop erties, irrespective of the part of the world in which they may originate. IMPORTANCE OF PHYSICAL PROPERTIES,. The outstanding physical characteristic of asbestos is its fibrous structure. Other im portant libers found in nature are those of animal origin, such as wool and silk, and those of vegetable origin, such as cotton and flax. In combustibility is one of the striking differences between asbestos and the fibrous products of animal or vegetable origin. Of perhaps equal importance is the difference in structure. Each filament of cotton, wool, or silk is of measurable and fairly constant diameter and is indivisible into finer sizes. On the other hand, fibers of chrysotile asbestos can bo divided and sub divided until a fineness is attained that is limited only by the delicacy of the machinery used and the skill of manipulation. The ulti CHAPTER 1. VARIETIES AND COMPOSITION OF ASBESTOS 5 mate fiber size is presumably the size of the ulti mate molecule or crystal lattice of asbestos. In other words, fiberization is a cleavage process, and cleavage in minerals is defined as a tend ency to spiit. in a certain direction, that is, to separate along and between layers of molecules. With respect to use, fiber size is important, and the size will depend upon the degree of fiberization attained in milling. Fibers ob tained from different deposits vary in the ease with which they may be fiberized. Thus, two samples of chrysotile asbestos, given exactly the same mill treatment, may furnish products differing considerably in fiber diameter, be cause one of them separates or fiberizes more easily than the other. Such differences may have great practical importance because an asbestos that is difficult to fiberize may require such intense milling to reduce the fibers to de sirable fineness that they may be broken into un desirable short lengths. Ease or difficulty of fiberization is therefore an important prop erty of asbestos. The use to which a chrysotile asbestos may be applied is governed largely by fiber length. The longest fibers command the highest prices and the shorter grades progressively lower prices. Apparently, therefore, primary at tention must be given to milling processes that will separate the fibers from the parent rock and will fiberize them adequately with a mini mum of fiber breakage. The heat, resistance of asbestos is important, in many applications. Some users of asbestos confuse nonflammability with refractoriness. Nevertheless, many substances that will not burn will melt or decompose at relatively low temperatures. The fireproof property of as bestos is one of its chief assets; but, although unburnable, it will decompose and lose its es sential physical properties at moderately high temperatures. Some students of the subject have conceived the idea that asbestos is a highly refractory substance by reading the statement made by Cirkel (1) that it can with stand temperatures of 2,000 to 3,000 F. easily, while some varieties can be subjected to a temperature of 5,000 F. with no apparent visible effects. With due respect to Dr. Cirkel, who wrote a splendid pioneer volume on a mineral of which little was known at that time, he was in error regarding the heat resistance of chrysotile. Brandenberger and coworkers (3), who have made a comprehensive study of temperature effects on chrysotile at the Mineralogical Insti tute of the University of Zurich, state that the so-called adsorbed wate'r of chrysotile is driven off at about 300 C. Between 550 and.600 C. all of the water of crystallization is driven off, and the mineral gradually 'alters to olivine. Accompanying this dehydration is a pro nounced change in physical properties. At 400 C. there'is a notable deterioration in fiber quality; and above 550 C., with more'`or less complete dehydration, chrysotile is completely decomposed. The amphibole varieties.of as bestos will withstand somewhat higher temper atures than chrysotile. However, crocidolite, although having a low water content, is easily fused into a black magnetic mass. BIBLIOGRAPHY 1. Cirkel, Fritz. Chrysotile Asbestos:.Its Occurrence, Exploitation, Minins?, and Uses. Canada Dept. Mines, Mines Branch, 2d ed., 1910, p. 30. 2. Sciiai.ler, \V. T. The Chemical Composition of Tremolite. Mineralogical Notes, Series 3. Geol. Survey Bull. (110,1910, pp. 133-130. 3. Brandenuerger, 15., Eppreciit, W., and Niooli, F. The Serpentine Minerals and Their Synthesis. II (trans. by Frank Riordan, Jr.). Helv. Chim. Acta, vol, 30,1947, pp. t>--14. 4. Raiiritt, John C. A New Study of the Anthopliyllite Series. Am. Mineral., vol. 33, May-June 1948, pp. 203-323. 5. Snaw, Myril C. The Asbestos Content of Asbestos Textiles. New Jersey Ceram. Res. Sta., Rutgers Univ., Mar. 27, 19130, 7 pp. 0. Vkrmas, F. I-I. S. The Amphibole Asbestos of South Africa (with discussion). Trails, and 1`roc. Geol. Soe. South Africa, vol. 55, 1952, pp. 199-232. 7. Bowi.es, Oliver. The Asbestos Industry. Bureau of Mines Bull. 552, 1955, p. S. CHAPTER 14. SUBSTITUTES FOR ASBESTOS INCENTIVES FOR SUBSTITUTE RESEARCH Shortage is a strong incentive for seeking substitutes. The general worldwide shortage of asbestos that existed during World War II and the early postwar period led to wide re search and experimentation on materials that might take its place. Germany's virtual isola tion from sources of asbestos prompted testing in that country of such possible substitutes as glass wool, steel wool, iron wire, synthetic rub ber, organic plastics, cellulose, and treated paper. Work on substitutes also was conducted with considerably intensity in the United States and several other countries. Expanded production and a reduction in mili tary requirements for asbestos by 1954 had brought supply and demand into approximate balance, and the progressive relief from short ages that characterized the years 1952 to 1954 led to a relaxation in efforts to find substitute products. Accordingly, there are few recent de velopments in this field. However, the major dependence of the United States upon foreign asbestos supplies, even though they are largely controlled by a traditionally friendly nearby nation, is a situation that demands constant awareness of the possibilities for substitution under emergency conditions. The merits of possible alternate products are therefore con sidered here. SODA-LIME-SILICA GLASS FIBERS AND MINERAL WOOL Glass and related fibers are manufactured in two basic forms--a short-liber woollike mate rial and a continuous filament. Rock wool, glass wool, and slag wool are used primarily as lightweight thermal insulation, such as house fill. Such applications, in general, are not sub stitutes for asbestos. Glass filaments made by more refined processes involving the use of platinum dies are of high quality and uniform size. Some of them are less than one-half mi cron in diameter and are adaptable to highly specialized uses, such as weaving into fabrics. Such filaments are used as substitutes for' as bestos in some applications. Glass fibers will not burn, but they will soften and coalesce when the temperature reaches a 02 certain point, which varies according to the composition of the glass. The heat and mois ture resistance of the glass filaments is limited bv the organic film applied to the individual fibers during manufacture to improve process ing and reduce breakage during subsequent ply ing and weaving operations. Without such a coating, the fibers are relatively brittle and self-abrasive. For high-temperature applica tions most of the organic film is removed by heating for a short time at about 300 C. (572 F.). The fibers are then recoated with a material suitable for the operating temperature. When glass filaments are used without such coatings, their properties are impaired to some extenCbut they will withstand temperatures up to 1,200 F., which is an advantage in certain applications. Normally, glass resists weathering very well. Windowpanes generally show no weathering ef fects, even after many decades of use. However, the surface area per unit volume of very fine glass fibers is so great that exposure to water vapor results in relatively rapid deterioration. Fiberglas is therefore less resistant than as bestos to the effects of steam or moisture. At tempts have been made to use glass fibers in place of asbestos in asbestos-cement products, but such tests have given unsatisfactory results, chiefly because of a chemical reaction between the glass and cement, which decomposes the libers and destroys their effective strength. Glass fibers are efficient thermal insulators in various types of equipment, such as stoves and refrigerators, where conditions are not corro sive. Tiie high tensile strength, the greater thermal stability compared wi}.h organic fibers, and the electrical resistance of glass fibers make them suitable for electrical insulation, such as sleeving for wire and tapes for the construction of some types of motors. Fiberglas is used in conjunction with, or as an optional alternate material for, asbestos in Navy shipboard cables. It is claimed, however, that the use of asbestos results in greater resiliency in finished cables Ilian can be obtained with Fiberglas. Glass fillers are permitted in specifications for cable filler (material that fills in the spaces in a group of insulated cables), but they have not yet been developed in a form that gives entirely satis factory cable performance, llecause of its high electrical and heat resistance, very thin glass- CHAPTER 14. SUBSTITUTES FOR ASBESTOS 63 fiber paper may find advantageous use in con densers for electronic equipment; for example, its use may make possible a reduction in the size of the condensers. A glass-asbestos cloth was designed during World War II to extend the supply of asbestos textile fibers. It has continued in use as a cov ering on thermal insulation applied to piping on naval vessels. It is woven with a plied yarn having one strand each of glass and asbestos yarn. Glass fabrics or combined glass-asbestos fabrics have some advantage over asbestos tex tile products because of lighter weight per square yard and greater strength, but they are generally inferior to asbestos "fabrics in resist ance to flexure, abrasion, and chemical action. Fabrics consisting of interwoven glass and as bestos yarns are now made in many weights and colors for- use as theater curtains and for fire proof draperies in schools, hospitals, libraries, lotels, and ships. Coarse glass fibers compressed into bats are efficient lightweight air filters that are used extensively for cleaning large volumes of air. Asbestos is not widely used in this field. The use of Fiberglas as a substitute for as bestos in friction equipment has, in general, given unsatisfactory results, chiefly because of the abrasive effects of glass on brakedrums. Also, the glass fabrics lack the high resiliency of those made of very finely divided asbestos filaments. During World War II and the Korean con flict a large part of the production of Fiberglas was applied to military uses. Many manufac turers of electric insulating materials, such as manufacturers of asbestos cloth and tapes, lami nates, varnished tubing, magnet-wire covering, and mica-insulating products, are listed as users of Fiberglas. Fiberglas was widely used dur ing World War II for heat, sound, and electric insulation on aircraft. Over 90 percent of the out put during World War II was used for mili tary or essential civilian use. Since it appears that Fiberglas can be substi tuted for asbestos in certain fields of applica tion, its future availability is of first impor tance. A question has been raised as to the adequacy of Fiberglas production facilities. The manufacture of Fiberglas in ultrafine fila ments was originally limited to a single plant operated by the Owens-Oorning Fiberglas Corp. Such a situation tends to impose a serious limi tation on the supply of an essential product in an emergency. With limited manufacturing facilities, the substitute product might be as difficult to obtain as the asbestos it is supposed to replace. 1 lowever, that situation no longer exists. The original company has enlarged its operations greatly; it manufactures Fiberglas in seven widely separated factories. Furthermore, seveial other companies now manufacture the product under license. It is believed that fa cilities will be adequate to meet- any reasonable demands that may develop in the near future. A question has also been raised as to lim itations on Fiberglas manufacture imposed by the need of platinum. At one stage in the process of Fiberglas manufacture the molten glass is drawn through perforations in a plati num-bottomed cell or bushing; apparently, no other substance can be substituted for the plati num so used. Because platinum is produced in limited quantities--a free-world production of about S00,000 troy ounces a year--and has* wide scientific and industrial use, its availability for wider application in this industry deserves care ful consideration. Platinum is a critical ma terial during war periods. Three important circumstances tend to relieve to some extent the threat of a possible shortage: 1. There is very little loss of platinum during the process of Fiberglas manufacture. The holes through which the fibers are drawn will gradually enlarge, and the platinum bushing will accordingly have to be rebuilt, using the same platinum. Care is taken to recover any dust or fragments of platinum. The first instal lation is the important consideration, but sub sequent replacement of losses is very small. 2. Research is being conducted constantly to find ways of reducing the quantity of platinum required in each bushing. Presumably, some saving is possible and will be accomplished. 3. Research is also being devoted to possible substitution of some less costly and more abund ant substance for platinum. Limited progress has been made, and there is at least some promise of success. Another raw material essential to Fiberglas manufacture that may be in short supply in times of emergency is cryolite, sodium-alumi num fluoride (Na:iAlF), which is mined only in Greenland. The supply, however, is aug mented by artificial cryolite manufactured from fluorspar. If supplies of both these materials are limited, sodium silicofluoride may be substi tuted. It has been produced as a byproduct from phosphate rock. HIGH-SILICA GLASS FIBERS Glass fibers approximating vitreous silica in composition arc superior to soda-lime-silica glass fibers in resistance to deterioration from the action of water vapor and to high tempera tures, but their manufacture is a difficult prob lem. Fused silica is extremely viscous at its melting point (1,728 C.),and its manufacture into thin filaments is very difficult. To over 64 ASBESTOS--A MATERIALS SURVEY come this high viscosity, fluxes ave added, the fibers are made, and the fluxes are then removed. Several methods are used, but they are similar in principle. First, filaments are formed from an easily workable composition, such as an alkali silicate. Second, the alkali or flux in the fila ment is removed by leaching or ionic substitu tion. The resulting Abel's are relatively porous and high in silica. They will withstand with little deterioration temperatures exceeding 1,000 C. The minimum diameter of highsilica fibers on which data were available in 1052 was about 2 microns, and the average was much greater. On the other hand, natural as bestos fibers are only a fraction of a micron in diameter. Correspondingly, the silica fibers are much less flexible than natural clirysotile. Be cause of their high moisture resistance and ability to withstand high temperatures, the vitreous silica filaments undoubtedly can be substituted for asbestos in some applications, but it is doubtful if they can replace asbestos where flexibility and elasticity are prime con siderations. Furthermore, the cost of manu facture is very high. High-silica-glass fibers are now made in much finer sizes than in 1952. Dr. Rudolf Lentz claims to be the inventor of a process for making synthetic asbestos in Ger many. His product, however, could not be callecl synthetic because its base was sodium silicate, and an analysis of the final product in dicated that it consisted of over 97 percent SiO,. It was, in fact, a silica-glass fiber. Three companies were licensed to manufacture this product in 194:1, but because of the military reverses suffered by Germany no progress was made (4).1 OTHER SILICEOUS FIBERS At least three companies are now making aluminum silicate fibers. They employ blowing processes, which do not require the use of plati num spinnerettes. Fusion may be accomplished with an electric arc. These fibers maybe em ployed whore exposed to temperatures of 2,000 F. or higher. They are costly to make and have special uses beyond the temperature ranges where asbestos products are employed. Fibers of pure quartz are now made in micron sizes. They are also costly and are applied only at high temperatures. ORGANIC SUBSTITUTES German scientists attempted to manufacture yarn from short-liber asbestos mixed with long organic libers, such as cotton, cellulose, or syn thetics, but the product obtained was very weak 1 ll.-iliWzi'il iidiiiIhtx in iwrPijfJii'xi-x refor to Items In the bibliuKi'ti|iliy nl (he ml of tliix elmplcr. (2). Cardboard with an organic plastic was used in Germany as a substitute for asbestos packing in flanges of steam and water pipes. This packing was satisfactory at pressures up to 5 atmospheres and temperatures up to 160 C. It is stated that substitutes for asbestos in highpressure packings have not been successful and that all substitutes developed and used up to 1944 were inferior to asbestos (1). A diaphragm of Perlon (synthetic fiber) paper coated with barite paste was tried by I. G. Farbenindustrie as a substitute for asbestos cloth as a diaphragm in a Stemens-Billiter cell in the manufacture of NaOHby electrolysis of NaCl solution. It failed within 30 minutes. However, a polyvinyl chloride diaphragm gave results equal to those obtained with asbestos cloth (5). Although reports are somewhat conflicting, polyvinyl fibers appear to be inferior to as bestos in asbestos-cement products. Silicone products alone or in combination with glass fibers have been used successfully as wire cover ing in certain applications. SUBSTITUTES FOR AMOSITE As indicated elsewhere, an important use for amosite is in the manufacture of light, fluffy insulation for use on marine turbines and jetplanes. The fluffiness appears to be a function of fiber diameter, the finer fibers showing the higher degree of thermal efficiency per unit weight. Accordingly, it has been found that Fiberglas having fiber diameters of less than 1 micron has a thermal efficiency comparable with that of amosite, but Fiberglas of this quality costs 5 or 6 times as much as amosite. Calcium silicate and diatomaceous-silica insulation prod ucts are used as substitutes for amosite in some applications. Clirysotile can be substituted for amosite in 85-percent magnesia products, with some in crease in weight per cubic foot and with a some what lower thermal efficiency. Ji. substantial substitution of clirysotile for amosite would, in some instances, increase the weight per unit volume beyond the limitations of military specifications. SUBSTITUTES FOR CROCIDOLITE Crocidolite was used widely for a time in making gas-mask filters. However, the Naval Research Laboratory found that, glass libers make superior gas filters. In gas-mask tests in a smoke-filled, room, it was found that only 1 particle in 100,000 passed through the Fibergins filter, and at the same time the mask caused no noticeable increase in normal breathing re sistance. The filter paper can be made in any CHAPTER 14. SUBSTITUTES FOR ASBESTOS 65 ordinary paper mill (5). Because of the success attained with Fiherglas air filters, the use of Bolivian crocidolite is no longer regarded as essential in this application. Because of its high resistance to chemical action, crocidolite has found wide use in mak ing acidproof packings. One of the newer plastics is now replacing crocidolite to an in creasing extent in this application, because it is stable up to 480 F., is resistant to acids and alkalies, and has low absorption. The chief use of crocidolite in the United States is in the manufacture of asbestos-cement pipe. Its principal assets are its free filterability and high strength. No satisfactory substi tutes are now available. Substitution of chrysotile for crocidolite in this application would, it is claimed, retard the drying time of the fab ricated pipes so greatly 'that plant capacity might be reduced as much as 50 percent. How ever, some of the harsh Canadian chrysotile fibers, such as those produced at the Munro mine, Ontario, can be substituted for blue as bestos to some extent. BIBLIOGRAPHY 1. Kranxich, W. I. G. Farbenindnstrie, A. G., Ludwigsliafen, PB-52025,1044, pp. 170-181. 2. Blakely, J. D., Dawson, E. L., Ga/.k, R,, and I-Iexdeksox, M. B. BIOS Final Kept. 404, PB 34022, 1945. 3. Liebexwirth. I. G. Fnrbeniudnstrie, A. G., Lndwigshafen, PLB-70305, FIAT, Keel B-31, fr. 40094-5,1945. 4. Field Information Agency. Technical and Scien tific Developments Relating to the Asbestos In dustry in Germany, 1947. FIAT Final Kept 1070. 5. Department op Defense, Office op Public Infor mation. Glass Fiber Filter Insulator Developed by Naval Laboratory. December 7,1950. ETHYL U .S. Asb : D es B u re ept to s au of Su r of In vfi t v eM-rini oen sr . In fo C ir 1959 B ow les