Hornblendes from Some Basic Hornfelses in the New England Region, New South Wales

R. A. Binns
Department of Geology, University of New England

Summary: With progressive increase in grade of contact metamorphism, alumi-nous hornblendes in some New England basic hornfelses change from a pale blue-green variety with ragged actinolitic habit, to a deeper bluish-green variety, then to a deeply coloured brownish type with granular habit. At all stages the coexisting plagioclase is appreciably calcic. No outer aureole of albite-epidote-actinolite hornfels has been recognized. The higher grade hornblendes are richer in alkalis and titanium, and poorer in octahedrally co-ordinated aluminium than those formed at low grades. Two analysed hornblendes display an unusual excess of calcium, which occupies the Y site, and another has a very high content of ferrous iron and potassium.

Mineralogical Magazine; 1965 v. 34; no. 268; p. 52-65; DOI: 10.1180/minmag.1965.034.268.04
© 1965, The Mineralogical Society
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