37© 



iKF.nr.Kic n. i. a ///•:/■: 



schists, tine conglomerate schists in which the pebbles and paste 



arc of similar whitish materials and the pebbles arc much sheared. 

 and schists o\ the texture of medium sandstones. The Last- 

 mentioned material ami some oi the liner conglomerate schists 

 looked so much like altered pyroclastics that they were called 

 tuffs in the field. (See description of the Parker Hill white schist. 

 below.) All these rocks are exposed more than once across the 

 strike. 



rhe porphyry schist that underlies the "schoolhouse con 

 glomerate" has an exceedingly tine groundmass, which is sericitic 



and in places rich in 

 chlorite. Thepheno- 

 crysts, ranging up to 

 nearly \ inch in diam- 

 eter, hut averaging 

 i ;\; i n c h . are of 

 quart z and plagio- 

 clase. They are uni- 

 formly distributed 

 and constitute about 

 half of the rock. The 

 quart/ has a very high 

 luster, is somewhat 

 bluish and very trans- 

 parent, and has tendency to break with a rude cleavage. The 

 plagioclase is so fresh that the striatums arc distinct and the frac- 

 ture surfaces are brightly reflecting. The shearing of the rock 

 seems to have been localized in the groundmass. Within its own 

 mass this schist has no bedding. 



The conglomerate schist ("schoolhouse conglomerate"), also, 

 is quite devoid of bedding. It contains many large and small 

 fragments of the porphyry schist, together with pieces of other 

 whitish rocks of the Lyman series, and masses of rust-brown. 

 smooth-looking schist, which are conspicuously darker than the 

 Lyman varieties. All the pebbles have been more or less sheared 

 and in such a way that their longest axes are parallel with the 

 dip of the cleavage. Some seem to have been roundish, but more 



Fte, a. -Lyman ("schoolhouse") conglomerate, 

 showing obscure outlines of pebbles, rhe dark masses. 

 edged with black enamel, arc of the One drab schist. 



Photograph by Mr. Savlcs. 



