lO 



J. SCHETELIG. 



M.-N. Kl. 



In the published tables of rock-analyses only very few examples are 

 given with the same composition as the plagioclase-granite from Mt. Betty. 

 For the sake of comparison I quote below from Osann's table ' the ana- 

 lyses No. 191 and No. 244, which nearly correspond with the plagioclase- 

 granite. 



100.43 



10037 



100.19 



No. 2 Plagioclase-granite, Mt. Betty. Anal. N. Sahlbom. 

 Osann No. 191 „Biotite-granite", Florence, Mass. Anal. L. G. Eakins. 

 — No. 244 „Granite", Rocklin, Placer Co., Gal. Anal. W. H. Mellville. 



The granite from Moores quarry, Florence, Mass. is described by 

 B. K. Emersg.n' "^ as a middle-grained fresh biotite-granite with small content 

 of muscovite. The rock is characterised by the great content of plagio- 

 clase and very small content of orthoclase and microcline. The prevailing 

 plagioclase shows the connection of this rock with tonalité (granodiorite). 



The granite from Rocklin, Placer Co., Cal. is described by W. Lind- 

 gren^: "The rock is of light-gray color and of medium fine grain. Grayish 

 quartz grains, white felspars sometimes with striation on the cleavage planes, 

 black or dark brown biotite, and silvery muscovite in small scales may 

 readily be distinguished with the naked eye." Under the microscope are 



^ A. Osann: Beiträge zur chemischen Pétrographie II 1905 

 ■•^ Memoirs U. S. G. S. XXIX p, 316. 1898. 

 3 Bull. U. S. G. S. 150 p. 172. 1898. 



