THE LYMAN SCHISTS OF NEW HAMPSHIRE 



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taken from different outcrops of the "schoolhouse conglomerate." 

 Microscopic examination revealed two distinct varieties. One is 

 composed largely of zoisite and bundles of parallel actinolite needles, 



with some chlorite and titanite and a 

 little plagioclase. The other is rich in 

 chlorite, plagioclase, and zoisite, and 

 contains titanite and a little epidote 

 and sericite. This schist is finely por- 

 phyritic, the phenocrysts being of 

 plagioclase (Fig. 12). Many have 

 been bent, sliced, or granulated by 

 the shearing. The white mica is 

 fairly well oriented and, together 

 with the other minerals, is inclosed 

 in an irregular background or net- 

 work of chlorite. There are some 

 chlorite aggregates which look as if 

 they had formed from a mineral that 

 was once present as phenocrysts. No 

 quartz is recognizable in either rock. 

 With reference to the origin of 

 these rocks, it would seem as if 

 their source was most probably igne- 

 ous. Some of them might have been 

 derived from sedimentary products of 

 incomplete decomposition, but they 

 can hardly have come from normal 

 argillitic material. 



Parker Hill white schist. — The 

 whitish schist that contains the dark 

 phyllitic fragments is composed prin- 

 cipally of quartz and orthoclase in 

 nearly equal proportions, somewhat 

 less plagioclase, and some chlorite and 

 sericite. The particles of quartz and feldspar have every gradation 

 in size from the largest to the smallest (Fig. 13) . There is relatively 

 little matrix, the larger grains being so numerous that they nearly, 



Fig. 11. — "Torn" plagioclase 

 phenocryst. The large dark area 

 in the middle of the photograph 

 is about one-third of the entire 

 crystal, the other two-thirds being 

 below the picture. The irregular 

 lower edge is the "torn" end. 

 Enlarged 20 diameters. 



Fig. 12. — Section of a pebble of 

 fine porphyry schist from the 

 "schoolhouse conglomerate" at 

 the Black Mountain locality. 

 Enlarged 16 diameters. 



