explajS'Ation of plate lxxix. 



Chabazite. 



Fig 1. Ben Lomond, N. S. \Vaies. Penetration twin on vertical axis. 



,, 2. Ben Lomond. Apex of cr_ystal in plan ; both segments of the twin 

 uonisist of three parts in parallel position. 



„ 3. Middlesex, Tasmania. Penetration twin on vertical axis. 

 Forms:— rt (1120), r (1011), e (0112), s (0221), f (1123). 



