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PROCEEDING OF THE ACADEMY OF 



[Vol. LXXIV 



ated with greenish-white crystals of willemite. The glaucochroite 

 is readily identified by the remarkable fact that the mineral is 

 bluish-green by daylight, but pink by artificial light. The largest 

 crystals measure 2 mm. in length. 



Four crystals were measured the results being given in Table I. 

 Six forms are new: r (130), z (270), d (101), k (Oil), 1 (131,) and 



Figs. 2-3. Glaucochroite, Franklin, N. J. 



y (122). The relative development of the faces and their position 

 are shown in figures 1 to 4. 



Three types of crystals occur; these will be designated below as 

 Types I, II, and III (figs. 1, 2, and 3, respectively). 



Type I (figure 1) is of rare occurrence, being limited to the 

 smaller cavities where the conditions were most favorable to perfect 

 growth The crystals show a well-developed prismatic zone, in 

 which there may be an oscillation of a (100), and m (110) ; terminat- 

 ed by a large, dull, and apparently etched dome, k(011); about 

 which is a prominent zone including d (101), e (111), f (121), and 

 1 (131). 



Type II (figure 2) shows also a well-developed prismatic zone 

 but the dominant terminal form is the pyramid f (121); h (021) and 



