Hostname: page-component-848d4c4894-hfldf Total loading time: 0 Render date: 2024-05-18T08:11:39.004Z Has data issue: false hasContentIssue false
  • English
  • Français

Crystallochemical classifications of phyllosilicates based on the unified system of projection of chemical composition: I. The mica group

Published online by Cambridge University Press:  09 July 2018

A. Wiewióra
A. Wiewióra*
Affiliation:
Institute of Geological Sciences, Polish Academy of Sciences, Al. Zwirki i Wigury 93, 02-089 Warsaw, Poland
Get access Rights & Permissions [Opens in a new window]

Abstract

A unified system of vector representation of chemical composition is proposed for the phyllosilicates based on projection of the composition, as given by crystallochemical formula, onto a field with orthogonal axes chosen for octahedral divalent cations, R2+, and Si (X, Y, respectively), and oblique axes for octahedral trivalent cations, R3+, and vacancies, □, (V, Z, respectively). Point coordinates for each set of axes were used to define the direction and length of the unit vectors for phyllosilicates belonging to different groups. Parallel to these fundamental directions the composition isolines were drawn in the projection fields. Applied to micas, this system enables control of the chemical composition by the general crystallochemical formula covering all varieties of Li-free dioctahedral and trioctahedral micas:

where z (number of vacancies) = (y-x+ m)/2; m (layer charge) =1; u+y+z = 3. There is a similar formula for vacancy-free lithian micas:

where w = m — x+y;m=1; u+y+w = 3, and for Li-free brittle micas:

where z = (y — x+m)/2; m = 2; u+y+z = 3. Projection fields were used to classify micas.

Type
Research Article
Information
Clay Minerals , Volume 25 , Issue 1 , March 1990 , pp. 73 - 81
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1990

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

Bailey, S.W. (1980) Structures of layer silicates. Pp. 1–124 in: Crystal Structures of Clay Minerals and their X-ray Identification (G. W. Brindley & G. Brown, editors). Mineralogical Society, London.Google Scholar
Burt, D.M. (1988) Vector representation of phyllosilicate compositions. Pp. 561–599 in: Hydrous Phyllosilicates (Exclusive of Micas) (S. W. Bailey, editor). (Reviews in Mineralogy, vol. 19). Mineralogical Society of America, Washington, DC. CrossRefGoogle Scholar
Burt, D.M. & Burton, J.H. (1984) Vector representation of lithium and other mica composition using exchange operators. Geol. Soc. Am. Abstr. Progr., 16.Google Scholar
Černy, P. & Burt, M. (1984) Paragenesis, crystallochemical characteristics and geochemical evolution of micas in granite pegmatites. Pp. 257–296 in: Micas (S. W. Bailey, editor). (Reviews in Mineralogy, vol. 13). Mineralogical Society of America, Washington, DC.CrossRefGoogle Scholar
Foster, M.D. (1960) Interpretation of the composition of lithium micas. US Geol. Surv. Prof. Pap., 354-E, 115–147.Google Scholar
Greenland, D.J. & Hayes, M.H.B. (editors) (1978) The Chemistry of Soil Constituents. Wiley & Sons, Chichester.Google Scholar
Guggenheim, S. (1984) The brittle micas. Pp. 61–104 in: Micas (S. W. Bailey, editor). (Reviews in Mineralogy, vol. 13). Mineralogical Society of America, Washington, DC.CrossRefGoogle Scholar
Newman, A.C.D. (editor) (1987) Chemistry of Clays and Clay Minerals. Mineralogical Society, London.Google Scholar
Thompson, J.B. Jr. (1982) Composition space: an algebraic and geometric approach. Pp. 141–188 in: Characterization of Metamorphism through Mineral Equilibria (J.M. Ferry, editor). (Reviews in Mineralogy, vol. 10). Mineralogical Society of America, Washington, DC.Google Scholar
Weaver, C.E. & Pollard, L.D. (1973) The Chemistry of Clay Minerals.(Developments in Sedimentology 15). Elsevier, Amsterdam.Google Scholar