210 Brush and Dana — Mineral Locality at Branchville. 



lated from our axial ratio compared with our measurements 

 and also with the measured angles of DesCloizeaux. It is 

 seen that the correspondence between our measured and calcu- 

 lated angles is not in alJ cases as great as could be desired, 

 although as much as could perhaps be expected from the nature 

 of the material. It has been stated that the crystals are often 

 grouped in parallel position, bnt as is common in such cases, 

 the parallelism is not perfect and furthermore the parts show 

 slight variations in position, even when the planes are smooth, 

 which are doubtless to be referred to the same cause. 



The habit of the Branchville crystals is short prismatic as 

 shown on figure 1 ; a basal projection of a more complex form 



is given in fig. 2. 

 The grouping in 

 parallel p o s i tion 

 gives rise to a repe^ 

 tition of the pris- 

 matic planes which 

 may result in a deep 

 striation or furrow- 

 ing of this face. 

 Besides this, the 

 zone of planes m, 

 ?, k, a, is often striated or channeled parallel to their common 

 direction of intersection. The crystals show rather perfect 

 cleavage parallel to the orthopinacoid. For analysis, carefully 

 selected portions of the purest crystals were taken by Prof. 

 Wells. The specific gravity was found to be 3*149. The 

 results are satisfactory as agreeing fully with those of Dam our 

 and leading to the same formula. For comparison we quote 

 Damour's analysis of the pale rose crystals which differs but 

 little from that of the yellow crystals ; it is to be noted that 

 the violet crystals (type I) have not been analyzed and it is 

 possible that some difference in composition may explain the 

 difference noted in the form. The Branchville mineral con- 

 tains a little less iron than the Limoges. 





Branchville. 





Limoges. 







G. 



=3-149 





rose, G.=3-185- 





I. 





II. 



Mean. 





P 2 5 



38-28 





38-44 



38-36 



•270 = 1-00 = 2 37-83 



FeO 



4-76 





4-37 



4-56 "063 ) 



8-7a 



MnO 



4229 







42-29 -596 



■•676 = 2-50 = 5 41-80 



CaO 



0-94 







0-94 0*17 ' 





HoO. 



12-25 





1215 



12-20 



•678 = 2-51 = 5 11-60 



Quartz 



1-76 









1-76 



Gangue 0-30 



100-11 



100-26 



