PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 605 



Hornblende schist. Granite.] 



Mic. The section is composed largely of quartz, feldspar (apparently orthoclase 

 and some acid plagioclase), biotite and chlorite, with a little epidote and pyrite. 



One section. 



Age. Archean. 



Remark. Nos. 929 to 932 were collected to illustrate mica schist and granite 

 and intermediate stages between these two rocks. Compare American Geologist, 

 vol. xx, pp. 41-48. v: s. G. 



No. 930. HORNBLENDE SCHIST (ivith granite). 



Same locality as No. 929. 



Ref. Annual Report, xv, pages 296, 297, 390. 



Mey. There are two samples of this number; one is a uniform, rather fine- 

 grained hornblende schist, rich in feldspar; the other is a dark amphibolyte in 

 contact with a pinkish granite. In the granite the hornblende is sometimes collected 

 in patches. 



Mic. The section' was evidently made from the granite. It consists essentially 

 of quartz, feldspar (apparently orthoclase and acid plagioclase), and green hornblende, 

 the latter mineral being collected on one edge of the slide. 



One section. 

 Age. Archean. u. s. G. 



No. 931. GRANITE. (Hornblendic.) 



Same place as No. 929. 



Ref. Annual Report, xv, pages 296, 390. 



Meg. A rather fine-grained, pinkish-gray, hornblende granite. 



Mic. An ordinary granite, the essential minerals being quartz, feldspar (appar- 

 ently orthoclase and acid plagioclase) and green hornblende. Chlorite, epidote, biotite 

 and sphene are also present. 



One section. 



Age. Archean. u. s. G. 



No. 932. GRANITE. 



Same place as No. 929. 



Ref. Annual Report, xv, pages 29G, 390. 



Meg. A rather coarse-grained, pinkish granite composed of quartz, feldspar 

 and a small amount of a dark mineral. 



Mir. A granite, composed mainly of quartz and feldspar. The latter mineral is 

 in three forms which are apparently orthoclase, acid plagioclase and microline. Horn- 

 hlaule seems to have been the ferro-magnesian constituent of the rock, but it was 

 in small amount and is now represented by chlorite. One section. 



Age. Archean. u. s. G. 



