The Variation of the 2¯01 Reflection in Plagioclases

D. L. Hamilton and A. D. Edgar
Department of Geology, The University, Manchester, England
Department of Geology, University of Western Ontario, London, Ontario, Canada

Summary: The position of the 2¯01 X-ray reflection in albite varies with the degree of Al/Si ordering. This is also true for binary plagioclases but the 2¯01 reflection for high-temperature plagioclases is constant and therefore independent of anorthite content. For plagioclases of ternary composition grown in a hydrous silicate melt, the position of the 2¯01 reflection gives a good estimate of the orthoclase content when a determinative curve is used that was originally drawn from data on high-temperature synthetic binary alkali feldspars.

Mineralogical Magazine; March 1969 v. 37; no. 285; p. 16-25; DOI: 10.1180/minmag.1969.037.285.02
© 1969, The Mineralogical Society
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