DIKE EOCKS OF SEPULCHRE MOUNTAIN. 129 



Table XII. — Mineralogical variations in the dike rocks of Sepulchre Mountain — Cont'd. 



Mineral 

 group. 



Speci- 



Phenocrysts other than feldspar. 



Mineral 

 group. 



Speci- 



Phenocrysts other than feldspar. 



nutn- 

 ber. 



Pyrox- 

 ene. 



Horn- 

 blende. 



Biotite. 



Quartz. 



num- 

 ber. 



Pyrox- 

 ene. 



Horn- 

 blende. 



Biotite. 



Quartz. 





482 

 ; 484 



Little. 



Much. 

 Much. 



Much. 

 Much. 





D 10 --..< 



504 

 505 





Much. 



Much. 



Much. 

 Much. 



Little. 

 Little. 





485 





Much. 



Much. 







508 





Much. 



Much. 



Much. 





486 



Little. 



Much. 



Much. 







509 





Much. 



Much. 



Much. 





487 





Much. 



Much. 







510 





Much. 



Much. 



Much. 





488 





Much. 



Much. 







511 





Much. 



Much. 



Much. 



r>» .... 



489 





Much. 



Much. 







513 





Much. 



Much. 



Much. 





490 





Much. 



Much. 







514 





Much. 



Much. 



Much. 





491 





Mucli. 



Much. 







515 





Much. 



Much. 



Much. 





492 





Much. 



Much. 





D„~~ 



518 





Much. 



Much. 



Much. 





493 





Much. 



Much. 







519 





Much. 



Much. 



Much. 





494 



(?) 



Much. 



Much. 







512 





Some. 



Much. 



Much. 





495 



(?) 



Much. 



Much. 







516 





Some. 



Much. 



Much. 



D 9 ...J 



496 

 497 





Some. 

 Some. 



Much. 

 Much. 







517 

 520 





Some. 

 Some. 



Much. 



Much. 



Much. 

 Much. 





500 



Much. 



Much. 



Much. 



Little. 





521 





Some. 



Much. 



Much. 





506 



Little. 



Much. 



Much. 



Little. 





522 





Some. 



Much. 



Much . 





507 



Little. 



Much. 



Much. 



Little. 





523 



' 



Little. 



Much. 



Much. 



D, 



498 





Much. 



Much. 



Little. 





524 





Little. 



Much. 



Much. 





499 





Much. 



Much. 



Little. 



D 12 .... 



525 





Little. 



Much. 



Much. 





501 





Much. 



Much. 



Little. 





526 





Little. 



Much. 



Much. 





502 





Little. 



Much. 



Little. 





527 





Little. 



Much. 



Much. 





503 





Much. 



Much. 



Little. 















Most of the pyroxene-andesites and hornblende-pyroxene-andesites 

 cany no biotite. In a few cases it is present in small amount. Some 

 hornblende-andesites contain neither pyroxene nor biotite; others have a 

 small amount of both. The structure of a glassy pyroxene-andesite dike 

 rock (421) is shown in PL XXII, fig. 1. In most of the hornblende-mica- 

 andesites there are no porphyritical pyroxenes ; they are present in small 

 amounts in a few cases ; and they are equally rare in the dacites. As quartz 

 phenocrysts increase in number biotite is more abundant, and hornblende 

 less so. Lime-soda feldspars are present in all the rocks, ranging- from 

 labradorite in the more basic andesites to oligoclase or andesine in dacite. 



The microscopical characters of the minerals are the same as in the 

 andesites of the breccias. The pyroxenes are hypersthene and augite, the 

 first being more readily decomposed and sometimes completely altered. 



MON XXXII, PX II 9 



