Growth Twinning in Phacolite

Mizuhiko Akizuki and Hiroshi Konno
Institute of Mineralogy, Petrology, and Economic Geology, Faculty of Science, Tohoku University, Sendai 980, Japan

Abstract: Phacolite from Mitaki, Sendai City, Japan, has a core of penetration-twinned chabazite. The crystal has a convex (0001) face on which many twin individuals are produced by a two-dimensional nucleation mechanism, resulting in complicated twinning during growth. Both the r and the r¯ (101¯1) faces repeat finely during growth because of twinning, resulting in {112¯3} sectors with polysynthetic twinning. Finally, single structures nucleate on the crystal edges [211¯] and develop along the (112¯3) face, penetrating each other near the centre of the face.

Keywords: phacolite • chabazite • zeolites • growth twinning • Mitaki • Japan

Mineralogical Magazine; September 1987 v. 51; no. 361; p. 427-430; DOI: 10.1180/minmag.1987.051.361.09
© 1987, The Mineralogical Society
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