Hostname: page-component-848d4c4894-5nwft Total loading time: 0 Render date: 2024-04-30T15:23:22.544Z Has data issue: false hasContentIssue false
  • English
  • Français

The thermal decomposition of amosite

Published online by Cambridge University Press:  14 March 2018

A. A. Hodgson ,
A. G. Freeman  and
H. F. W. Taylor
A. A. Hodgson
Affiliation:
Cape Asbestos Fibres Limited, Barking, Essex
A. G. Freeman
Affiliation:
Cape Asbestos Fibres Limited, Barking, Essex
H. F. W. Taylor
Affiliation:
Cape Asbestos Fibres Limited, Barking, Essex
Get access Rights & Permissions [Opens in a new window]

Summary

When amosite (fibrous grunerite, Fe5·5Mg1·5Si8O22(OH)2), is heated in argon or nitrogen, physically combined water is lost up to 500–700° C. Above 500° C (static) or 700° C (dynamic), dehydroxylation occurs endothermically, giving a pyroxene as the main product. Under dynamic heating conditions, part of the hydroxyl water is lost as hydrogen, with concurrent oxidation of the iron. At about 1000° C the pyroxene is decomposed to olivine and cristobalite; at about 1100° C melting begins. In oxygen or air, physically combined water is again lost below 500–700° C. At 350–1200° C a sequence of overlapping dehydrogenation, oxygen absorption, and dehydroxylation reactions occurs, which gives rise to a broad exotherm on the d.t.a. curve. The main products (for static heating conditions) are an oxyamphibole at 350–800° C, and a spinel, hematite, a pyroxene, and X-ray amorphous material at 800–1100° C. Silica crystallizes as cristobalite at 1100–1350° C, and as tridymite at 1450° C. Most of the products in either neutral or oxidizing atmospheres are formed topotactically. The mechanisms and rates of the reactions are discussed, and the problem of determining the chemically combined water in amosite and other minerals of similar composition is considered.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 35 , Issue 271 , September 1965 , pp. 445 - 463
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1965

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Addison, (C. C.), Addison, (W. E.), Neal, (G. H.), and Sharp, (J. H.), 1962. Journ. Chem. Soc., p. 1468.Google Scholar
Barnes, (V. E.), 1930. Amer. Min., vol. 15, p. 393.Google Scholar
Basta, (E. Z.), 1957. Min. Mag., vol. 31, p. 431.Google Scholar
Bowen, (N. L.) and Schairer, (J. F.), 1935. Amer. Journ. Sci., ser. 5, vol. 29, P. 151.Google Scholar
Brindley, (G. W.) and Yovell, (R. F.), 1953. Min. Mag., vol. 30, p. 57.Google Scholar
Brown, (G. M.), 1960. Amer. Min., vol. 45, p. 15.Google Scholar
Flood, (P.), 1957. X-ray powder data file, 7th set, card 7-394. Amer. Soc. Testing Materials, Philadelphia.Google Scholar
Freeman, (A. G.) and Taylor, (H. F. W.), 1960. Silikattechnik, vol. 11, p. 390.Google Scholar
Ghose, (S.) and Hellner, (E.), 1959. Journ. Geol. (Chicago), vol. 67, p. 691.Google Scholar
Heystek, (H.) and Schmidt, (E. R.), 1953. Trans. Geol. Soc. South Africa, vol. 56, p. 149.Google Scholar
Hodgson, (A. A.), 1963. Ph.D. thesis, London.Google Scholar
Hodgson, (A. A.), Freeman, (A. G.) and Taylor, (H. F. W.), 1965. Min. Mag., vol. 35, p. 5.Google Scholar
Patterson, (J. H.), 1965. Min. Mag., vol. 35, p. 31.Google Scholar
Taylor, (H. F. W.), 1962. Clay Min. Bull., vol. 5, p. 45.Google Scholar
Vermaas, (F. H. S.), 1952. Trans. Geol. Soc. South Africa, vol. 55, p. 199.Google Scholar