IGNEOUS ROCKS FROM THE ORTIZ MOUNTAINS 235 



Andose. II. 5. 3. 4 (Diorite) 

 This rock is in most respects identical with the preceding types 

 but differs in having a tendency toward a porphyritic texture. It 

 forms the massif of Lone Mountain, a partially isolated peak to the 

 southeast of the Ortiz group. Its consanguinity with the main stock 

 is evident from the analyses. Two of these were made, from the 

 top and side respectively, and these are given in the preceding table. 

 They are placed next the Akerose for comparison, this latter type 

 being most closely related chemically and also the nearest in space. 

 The most noteworthy differences are the higher lime and lower potash 

 of the Andose. 



EssExosE. II. 6. 2. 4 (Diorite and Essexite) 

 This rock type is an exceedingly common one, and is somewhat 

 variable. It forms the outlying hills on the southeast, and usually 

 forms the top of those with an altitude of about 8,300 feet. It is 

 from one of these that X is taken. IX is from the top of the highest 

 mountain. The recalculated analysis requires nepheline. This is 

 sometimes present in the slides; more often a porphyritic structure 



TABLE VI 

 Chemical Composition of Essexose 



