Optical Data on Some Authigenic Feldspars from Western Australia

J. E. Glover and P. Hosemann
Department of Geology, University of Western Australia, Nedlands, Western Australia
West Australian Petroleum Pty. Ltd., Box C1580, G.P.O., Perth, Western Australia

Summary: Authigenic envelopes up to 0·18 mm thick on clastic potassium feldspar grains from arkoses and subgreywackes of the Devonian Nannyarra Greywacke have been examined with the four-axis universal stage. The plane of the optic axes is parallel to (010) in some segments of individual envelopes and normal to (010) in others, and the range of 2Vα over all envelopes is from close to 0° to 65°. The optics are ascribed to modifications of potassium feldspar corresponding to high-and low-sanidine and orthoclase.

Mineralogical Magazine; March 1970 v. 37; no. 289; p. 588-592; DOI: 10.1180/minmag.1970.037.289.08
© 1970, The Mineralogical Society
Mineralogical Society (www.minersoc.org)