Ford — Neptmiite Crystals from. San Benito Co., Cat. 237 



observed this face was dull in luster and distinctly curved, and 

 only approximate measurements could be obtained from it. 

 Its symbol was determined, however, by its zonal relations, for 

 it was found to lie at the intersection of the pyramid zone 

 a (100) -s (111) -a (111) -i?(311) -a (100) and the zone m (110) 

 — ^(112) — m (110). This form g is new to the mineral, for 

 although Boggild in_Mineralogia Groenlandica, page 506, lists 

 such a form as p (211) it is evidently a misprint, for in the 

 original article by Wallenstrom* the form referred to is given 

 as p (311). The various forms were identified by the follow- 

 ing angles : 





Meas. 



Calc. 



a (100) /s jn(llO) 



49° 52' 



49° 53' 



a (100) /v c (001) 



64° 22^' 



64° 22' 



01(110) ^ s (111) 



38° 0' 



37° 58' 



02(100) /s c (001) 



73° 49' 



73° 49' 



02(110) ^ i (112) 



78° 26' 



78° 23V 



01(110) /s o (111) 



55° 14' 



54° 58' 



rn(llO) ^ g (211) 



40° 2' 



40° 28^' 



a (100) /v p (311) 



39° 38^ 



39° 27' 



igure 5 shows in stereographic projection 



all the crystal 



hiqioy 



mO'o) 



a ooo) 



forms of neptunite that have been listed. Those observed on 

 the Greenland crystals are indicated by solid dots, while the 



* Loc. cit. 



