214 Brush and Dana — Mineral Locality at Branchville. 

 And the measured and calculated angles are : 





Calculated. 



Measured 



001^051 = 



79° 15' 



79° 



001 ~103=r 



12 50 



13-14 



Optically we find the crystals as before stated to be biaxial, the 

 optic axes being situated in the clinodiagonal section and the 

 bisectrix nearly normal to the cleavage-face ; the double refrac- 

 tion is negative and the axial angle large. 



Besides the crystals occasionally appearing in the cavities, 

 and often united in slightly diverging groups with edges par- 

 allel to b projecting, the mineral occurs foliated to almost 

 massive and granular, the folia, however, usually distinct and 

 often grouped in rosettes or stellate forms. 



Dickinsonite is the species about whose composition we felt 

 most doubt when we first published. The material then in 

 hand was very scanty and not entirely pure, and although ex- 

 cellent analyses were made by Pen field, their interpretation 

 was a matter of some doubt because of admixture of more or 



P 2 5 



FeO 



MnO. 



€aO 



MgO 



Na 2 



K 2 



Li 2 



H 8 



Quartz 



I. 

 39-57 



31-74 

 215 



7-47 

 1-49 

 0-20 

 1 66 



2-58 



Dickinsonite, Branchville. 



Analysis of first sample. 

 Sp. Gr. 3-143, 

 II. Mean. 



39-57 -f- 142 : 



13-25 13-25 -f- 72 ■■ 

 31-42 31-58 h- 71 

 2-15 H- 56 : 



trace 



7-44 

 1-55 

 0-14 

 1-65 

 2-58 



7-46 

 1-52 

 0-17 

 1 65 



2-58 



62 

 94 

 34 

 18 



2= 



•279 

 •1841 

 •445 

 •039 



•124 

 •017 

 •005 

 •094 



=1-00=1 



^•814 =2-92=3 



= 0'34=* 









99-93 













Analysis 



of second sample. 







I. 



II. 



Mean. 







P 2 5 



40-89 





40-89 - 



- 142 = 



•288 =1-00 = 1 



FeO 



12-96 







12 96 - 



- 72 = 



•180] 





MnO 



31-83 



* . 



3183 - 



- 71 = 



•448 





CaO 



2-09 



» • • - 



2 09 - 



- 56 = 



•038 





MgO 



none 













* -811=2-82=3 



Na 2 



.... 



7-37 



7-37 - 



- 62 = 



•120 





K 2 



_ 



1-80 



1-80 - 



- 94-2= 



•019 





Li 2 





0-22 



0-22 - 



- 34 = 



•006 





H 2 



1-64 



1-62 



1-63 - 



- 18 = 



•092 =0-32=i 



Quartz 



0-85 



0-79 



082 









9961 



less eosphorite as well as quartz. Two independent sets of 

 new analyses have been made by Professor Wells. The ma- 

 terial for the first was picked with great care, but in order to 



