226 



University of California Publications. 



[Geology 



of linarite from this locality were made by Rogers (Mineralogical 

 Notes, Amer. Journal Sci. 1901, (4), 12, 42), and his crystals 

 showed only a few forms. 



In the orientation of Kokscharov, as given by Dana, the 

 broader prominent plane, parallel to which most of the crystals 

 are tabular, is taken as the base, whereas Goldschmidt in his 

 " Winkeltabellen " reverses the crystals and makes the rear dome 

 (101), the base. There appears to be no advantage in changing 

 the orientation as given by Dana and it is therefore followed 

 here. The crystals are very small, but show a good zone of ortho- 

 domes with minute faces on the edges formed by the domes and 

 unit prism. A measurement of one of the best of the crystals, 

 which appeared to be a simple crystal, showed by the symmetry 

 that it was twinned on the orthopinacoid. Fig 1 (pi. 19) is an 

 orthographic projection on the base of this twinned crystal with 

 the lower faces shown in clotted lines, and fig'. 2 is the clino- 

 graphic drawing from this projection to illustrate the general 

 habit and combination of forms. 



Fifteen forms were found, of which three are new for linarite. 



c (001) o (203) ir (012) i (716) new 



a (100) s (T01) r (011) Jc (211) new 



m (110) x (302) q (Tl2) // (14.0.1) new 



I (210) u (201) g (211) 



Rogers gives (010) on his crystal, but the clinopinacoid was not 

 observed by the writer. 



A calculation of the elements for linarite based on the axial 

 ratio a:b:c = 1.716: 1: 0.8296, /? = 77° 23' gives 



p o = 0.4834 p' Q = 0.4954 e = 0.2184 



q" = 0.8096 q' = 0.8296 e' = 0.2239 



^0 " o 



The reading's on the separate faces are given in the following - 

 table, the faces underscored being in twinned position. 



Measured Calculated 

 <P P 4> P 



001 



90°00' 



12°40' 



90°00' 



12°37' 



00T 



90 00 



12 44 







100 



90 00 



90 00 



90 00 



90 00 



100 



90 00 



90 00 



90 00 



90 00 



110 



30 55 



90 00 



90 00 





