36 NEW YORK STATE MUSEUM 



36 Datolite from Westfield Mass. Stereographic projection show- 

 ing zonal relations of occurring forms. 



37 Datolite from Westfield Mass., showing typical crystal habit. 

 Forms: a (100), x (102), v (103), c (001), b (010), m x (on), g 

 (012). t (013), O (018), m (no), o (120), n (in), v (in), e 

 (ii_2), A (113), (x (114), k (115), Q (122), p (121), a (124), 

 i (123), M (122), e' (148), A.' (149), /a' (1.4.10); the last three 

 are new to the species. 



38 Datolite from Westfield Mass. Basal projection of figure 37. 



39 Datolite from Westfield Mass., enlarged projection of a portion 

 of figure 37, viewed in reversed position to show the position 

 of the new planes. 



40 Datolite from Westfield Mass. Penetration twin parallel to 

 a (100) ; having c for the twinning axis. The faces g and a are 

 composition planes. 



