Growth twinning in phacolite

Abstract

AbstractPhacolite 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 faces repeat finely during growth because of twinning, resulting in {112̄3} sectors with polysynthetic twinning. Finally, single structures nucleate on the crystal edges [211̄] and develop along the (112̄3) face, penetrating each other near the centre of the face.