A QUANTITATIVE MINERALOGICAL CLASSIFICATION 

 OF IGNEOUS ROCKS-REVISED 



ALBERT JOHANNSEN 



University of Chicago 



PART II 



CLASS 2, ORDER I 



(210) Meso-silexite. See note under (no). 



(211) Moyite. The rocks of this family are quartz-ortho- 

 granites. Since three of the rocks described by Daly^ from the 

 Moyie sill along the Forty-ninth Parallel are of this uncommon 

 type, the term mojdte is here suggested for the family name. 



(215) Rockallite Judd. The name rockallite is derived from 

 the Island of Rockall, off the coast of Ireland. Judd^ describes 

 the rock as composed of aegirite, quartz, and albite. While the 

 presence of aegirite makes the rock abnormal, the term may be 

 used, at least temporarily, for the family name. Rockallite is a 

 quartz-rich aegirite-albite-tonalite. 



(216) Orthogranite. This is a comparatively rare rock, 

 only differing from normal granite in containing no plagioclase. 

 In this group also belong anorthoclase-granite, potash-rhyoUte 

 (orthorhyolite) , comendite, and some grorudites and solvsbergites. 

 Many of the granites belonging here are aegirite- or riebeckite- 

 bearing. For the use of the prefix "ortho-" see (in). 



MicrocHne-granite . 



Anorthoclase-granite. 



Orthogranitite. 



'Reginald A. Daly, "Geology of the North American Cordillera at the Forty- 

 ninth Parallel," Geol. Surv. Canada, Mem. 38, Part I, pp. 229, 230, 231. 



^ J. W. Judd, "On the Petrology of Rockall," Trans. Royal Irish Acad. Dublin, 

 XXI (1897), 49-57. 



158 



