3i0 



F. L. Bansome — Apatitic Minette. 



The wyomingite is in the perpotassic subrang and the shonk- 

 inite in the sodipotassic subrang of the wyomingase rang. 



None of the minettes of which reliable chemical analyses 

 are available falls near Washington ose in the quantitative clas- 

 sification. The three rocks of this type included in Washing- 

 ton's tables contain from 50*81 to 52*26 per cent of silica. 

 Consequently they are all in the dosalane class. Owing to 

 their relative richness in silica and alumina as compared with 

 the rock here described, their norms are more feldspathic and 

 all are in the perfelic.or Germanare order. These norms, from 

 the tables, are as follows : 



Norms of Minettes. 

 I II 



Or 



22*8 



Ab 



23-6 



An 



14-2 



Ne 



Di 



14*8 



Hy 



01. _. 



Mt _. 



I'O 



8-0 



3-9 



11 



l.-l 



Ar> ._. 1-1 



320 

 9-5 



53 



III 



41-4 



8-4 

 16*1 



5*6 

 5-1 



3'2 

 2 5 



3*9 

 5-4 

 14-7 

 3-5 

 3-2 

 1-4 



I. Augite-minette (Pirsson). Monzonose. W. T. Prof. Paper 

 14, p. 255. 

 II. Soda-minette (Brogger). Akerose. W. T., p. 263. 

 III. Augite-minette (Doss). Dopotassic subrang of andase. W. 

 T., p. 265. 



All of these norms contain considerable albite, the quantity 

 reaching 23*6 per cent in the augite-minette (monzonose) from 

 the Little Belt Mountains, Montana, described by Pirsson (I), 

 whereas in the washingtonose here described there is no norma- 

 tive albite. The three norms just given also contain much more 

 anorthite than that of the rock from the banks of the Colum- 

 bia, but show no normative leucite. Other differences will 

 appear in comparing these norms with that of washingtonose. 



The actual mineralogical composition, or mode, of the wash- 

 ingtonose described can not be accurately calculated, as the 

 compositions of the augite and biotite are not known. The 

 abundance of lenads in the norm, conditioned by the low silica 

 and high alkalies, suggests modal nephelite. None, however, 

 has been detected, while it is certain, on the other hand, that 



