Lithium-Aluminium Micas from the Meldon Aplite, Devonshire, England

M. Nawaz Chaudhry1 and R. A. Howie
Department of Geology, King's College, University of London
1Present address: Department of Geology, University of the Panjab, Lahore, Pakistan.

Summary: Chemical analyses of sixteen lithium-aluminium micas are presented along with their optical, physical, and X-ray data. Compositional variation, substitution relations in structural positions, and octahedral occupancy are discussed. The 2M2 structural types are found to crystallize in volatilerich low-temperature environments whereas the 1M polytypes occur in comparatively volatile-poor and higher-temperature environments. Variation diagrams have been constructed to show the relationship between octahedral sites occupied by (Fe2++ Fe3++13Mn+Ti) and refractive indices and specific gravities.

Mineralogical Magazine; September 1973 v. 39; no. 303; p. 289-296; DOI: 10.1180/minmag.1973.039.303.05
© 1973, The Mineralogical Society
Mineralogical Society (