ransome: albitite dikes 117 



The mineralogical composition as calculated from this analysis 

 in accord with the microscopical examination, the small quantity 

 of potash being included in the albite, is as follows: 



Albite (approx. Abg6 Ani) 76 5 



Calcite 9.2 



Quartz ." 8.8 



Kaolinite ' 3.5 



Anatase 0.8 



Apatite 0.4 



Water 0.8 



100.0 



The calculation of the norm in order to find the place of the 

 rock in the American quantitative system presents some difficul- 

 ties, owing to the presence of the calcite. If the calcite were 

 calculated as such it would place the rock with beerbachose in 

 the dosalane class, where it evidently does not belong. If the 

 carbon dioxide be disregarded and the analysis recalculated to 100, 

 the derived norm shows an excess of calcium in the form of over 

 9 per cent of calcium metasilicate. In other words there is not 

 enough alumina to combine with all of the alkalies and lime as 

 feldspar. The norm on this basis falls in the unnamed persodic 

 subrang of the alkalicalcic rang of the canadare order of the per- 

 salane class. On the other hand if both the carbon dioxide and 

 the calcium oxide be rejected, the analysis recalculated to 100, and 

 the norm then computed, the rock falls into the subrang tuolum- 

 nose in company with the somewhat similar soda-syenite porphyry 

 of Tuolumne County, California, described by Turner 2 and the 

 soda syenite or albite diorite 3 of Douglas Island, Alaska. This 

 appears to be its natural as.sociation and the tentative calculation 

 of the three norms, by showing that the lime is in excess of the 

 quantity that can be combined with the available alumina to 

 form feldspar, indicates either that the calcite is an original mineral 

 (which the microscope disproves) or that the calcite has been 



* Turner, H. W.: Further contributions to the geology of the Sierra Nevada, 

 17th Ann. Rept. U. S. Geol. Survey, Part I, p. 665. 1896. 



3 Spencer, A. C: The Juneau gold belt, Alaska. Bull. U. S. Geol. Survey 

 Xo. 287, pp. 99-105. 1906. 



