202 



University of California. 



LVol. a. 



E = — f = 1 335 1 . This form was noted but once as a long 

 narrow face. The face is in the zone c m . 



I) = — 2= { 221 \ . This form occurs on two crystals. The 

 reflections in both cases were fair. 



tr = — 12 = 1 121}.. A small face represents this form. 



The base and the unit prism are the predominating forms, 

 the other forms being subordinate in size. The common habit 

 is long prismatic. Most of the crystals show only the two forms 

 c and m. The crystals measured and shown in Figures 4-7, 

 Plate 19, are not so long, and consequently deviate slightly from 

 the common long prismatic habit. 



Seventeen crystals were measured, of whieh two showed only 

 the unit prism faces, both ends being broken off. Many more 

 were examined with a lens, but no other forms were seen. The 

 combinations seen on these crystals are shown in the following 

 table : 



No*' c bah fmlwvg t o r 7r E D <r 



1 c — — — f m — — — o — 7r — D — 



2 c — — m — — — g — 



3 c li — in J t — r 



4 c m t E 



5 C b III W O 7T — 



8 c m t 



9 c b — m — — — — — o — 7t — 1> — 



10 m 



11 c 6 m 1 



12 m 



13 c b m 



14 — b — h — m I 



15 c — a h — m I — — — — — — — cr 



17 c — a — — in — — c — — — — — — — — 



All of the forms observed by Des (Jloizeaux were noted on 

 these crystals, except — f = \889\ and — = {5.5.22}, which 

 are probably vicinal. 



In the following table the values are derived from the 

 measurements by the writer, and show a slight difference from 

 those given bv Goldsehmidt: 



