The Shinumo Area. 383 



cleavage is rather distinct. The texture ranges from fine to 

 coarse. To the unaided eye both the quartz and mica are visi- 

 ble. Under the microscope the rock is seen to be composed 

 of interlocking grains of quartz, with an almost equal amount 

 of mica. The mica flakes are arranged in parallel lines. The 

 greater part of the mica is muscovite, with occasional flakes of 

 brown biotite. 



Locally the schist is garnetiferous, and in one locality tour- 

 maline was observed. All gradations between the quartzose 

 and the micaceous phases occur, but in no instance does the 

 mica exceed the quartz in quantity. 



The quartz-hornblende schist is dark green in color. The 

 cleavage is imperfect, and the texture fine-grained and uni- 

 form. The rock is dense and hard. The mineral constituents 

 cannot usually be distinguished in the hand specimen without 

 the aid of the lens. Under the microscope the rock is seen to 

 consist of about equal proportions of quartz and green horn- 

 blende. The quartz is present in interlocking grains. The 

 hornblende tends to form automorphic crystals whose longer 

 axes have a roughly parallel arrangement. No other minerals 

 were present in the slides examined. In some phases of the 

 rock the quartz exceeds the hornblende in amount. 



The hornblende schist is dark green in color. It is a soft 

 rock, considerably disintegrated, and crumbling under the 

 hammer. The texture is coarse granular. Megascopically the 

 rock appears to consist almost entirely of dark green horn- 

 blende. No schistose structure is observable in the mass. 

 The microscope shows the rock to consist almost wholly of 

 large crystals of green hornblende in all stages of alteration. 

 A small amount of interstitial quartz occurs. The quartz 

 granules are strung out in a roughly parallel fashion. The 

 rock is badly altered and the thin section is unsatisfactory. 



The quartz-diorite found in the river gorge eastward from 

 the cable crossing is a coarse-granular rock of typical granitic 

 texture. It is a hard, resistant rock, which tends to weather 

 into roughly angular blocks, a feature that distinguishes it in 

 the mass from the exposures of the schists. The minerals visi- 

 ble to the unaided eye are white striated feldspar, dark horn- 

 blende, and glistening black biotite. The color of the rock is 

 dark grey and the appearance is remarkably fresh. The tex- 

 ture is uniform throughout the exposures observed, and the 

 rock is apparently without contact modifications. No ten- 

 dency to gneissoid banding was observed. 



Under the microscope it is seen to be a coarse-granular rock 

 of granitic texture. The dominant mineral constituents are 

 plagioclase and common hornblende. The plagioclase ranges 

 from oligoclase to labradorite. Microcline, orthoclase, and 



