282 



C. ANDERSON. 



Schrauf's elements. Farrington was, I believe, the first to 

 remark on this variation; in his study of the azurite of 

 Arizona, 1 he points out, for example, that the measured 

 angle m\m closely approximates to 81° 8' instead of 80° 42' 

 as calculated by Schrauf. Farrington was not able to say 

 " whether this variation is to be regarded as a fundamental 

 difference in the prismatic angle of the crystals from the 

 separate localities, or, on the other hand, as so small as to 

 be within the limits of error of observation." Evidence 

 has now accumulated which shows that there is a funda- 

 mental difference, and that Schrauf's elements, though 

 correct no doubt for the azurite of Ohessy, are not the best 

 for crystals from other localities such as Arizona, Broken 

 Hill, N. S. Wales, 2 Muldiva and Girofla Mines, Queensland,* 

 Tsumeb, German S.W. Africa, 4 and Oalabonna, Sardinia. & 

 In all these cases the variation from Schrauf's angles is 

 considerable and in the same direction, which would lead 

 to the conclusion that the azurite of the type locality 

 Ohessy is abnormal. 



A large number of reliable angles were obtained from 

 measurement of the crystals described in this paper, and 

 by carefully sifting them and rejecting all except those 

 derived from single and distinct reflections, the figures 

 tabulated below resulted: — 







4> 





P 





1 



Form. 



Average. 





Limits. 



Average. 





Limits. 



Obs 

 20 



c (001) 



o / // 



90 



o 



/ o / 



2 24 42 







2 



22- 2 27 



m (110) 



49 241 



49 



17-49 29 



90 



89 



57-90 3 



56 



w{U0) 



30 18 



30 



14-30 22 



5» 



89 



56 - 90 2 



16 



7><021) 



1 23 



1 



20- 1 27 



60 33 21 



60 



30-60 37 



14 



/(Oil) 



2 441 



2 



42 - 2 49 



41 34 



41 



28-41 39 



17 



I (023) 



4 4£ 



4 



0-4 7 



30 38 



30 



33-30 42 



10 



#(241) 



29 47 



29 



44-29 49 



76 14 



76 



13-76 20 



17 



k (221) 



48 50 



48 



47-48 53 



69 37 



69 



34-69 39 



14 



s (111) 



50 35 



50 



34 - 50 36 



54 211 



54 



19-54 26 



4 



P (223) 



51 4 24 



51 



1 -51 8 



43 16 36 



43 



13-43 20 



5 



1 Farrington, Amer. Journ. Sci., xli, 1891, pp. 300-307. 



2 Steiner, Ann. Mus. Nat. Hung, iv, 1906, pp. 293 - 298; Cohen, Journ. 

 Roy. Soc. N.S. Wales, xliv, 1910, pp. 577-583. 



3 Anderson, Rec. Austr. Mus., vu, 1909, pp. 278 - 279. 

 1 Toborffy, Zeits. Kryst. lii, 1913, pp. 225 - 235. 



5 Manasse, Atti d. Soc. Tosc. Sc. Nat., xxix, 1913, pp. 196-209. 



