Lawson.] 



Geology of Carmclo Bay. 



1 1 



some attained a size of 1.5 mm., and one was found to be as much 

 as 3 mm. in greatest length. Of these inclusions the feldspars usu- 

 ally present sharply idiomorphic forms, and are frequently twinned. 

 The quartzes occur prevailingly in rounded bleb-like crystals, some- 

 times angular, and recall the rounded quartzes of the quartz- 

 porphyries. The biotite has the form of thick little plates, which 

 show sometimes hexagonal sections. The muscovite occurs in 

 ragged, shred-like patches. Minute slender needles, probably apatite, 

 also occur in the phenocrysts, but these are scattered in all directions 

 and do not appear to have any definite relation, as to their orien- 

 tation, to their host. 



Figure 2. — Section of orthoclase phenocryst ot Santa Lucia granite, parallel 

 to basal pinacoid (001), showing inclusions of quartz, q; felds- 

 par, f; biotite, b; and muscovite, m. All the quartzes have 

 a common orientation, with the optic axis perpendicular to the 

 basal pinacoid of the host; and the feldspars have a common 

 orientation by groups, x 8. 



The orientation of the quartzes and feldspars is very remarkable. 

 Not only are these minerals distributed in their host in definite 



