LITHOLOGY. 233 



for mica. It is therefore composed of quartz, or quartz and feldspar, 

 mixed with chlorite. It is light green in its color, and does not possess 

 the soft feel and glistening lustre that characterize the micaceous schists. 

 It is a common rock; but though the proportion of ingredients may vary- 

 widely, and accessories may be present, the rock always has the same 

 color and appearance. It is always fine in texture, and none of the 

 ingredients are macroscopically recognizable. It is easily distinguished 

 from the hornblende rocks, because, in all the amphibolites, fibrous or 

 radiated crystals, which prove on examination to be hornblende, are 

 always macroscopically recognizable. 



A variety of this rock from Pittsburg, when microscopically examined, 

 is characterized by the presence of much plagioclase in minute grains. 

 Chlorite, orthoclase, quartz, and epidote make the rest of the rock. The 

 chlorite is distinctly foliated, and assumes brilliant colors in polarized 

 light. Another specimen from Connecticut lake in the same town con- 

 tains more quartz, less plagioclase, and much pyrites, and is otherwise 

 the same. 



A variety from Diamond pond in Dixville consists mainly of chlorite 

 and quartz, and contains hornblende, titanic iron, epidote, and calcite, as 

 accessories. Calcareous chlorite schists are not uncommon ; and when- 

 ever the calcite is in grains of sufficient size to show any properties, the 

 polysynthetic structure of the grains, which has been shown to be caused 

 by pressure, is very conspicuous (see p. 128). 



A variety from Lebanon is dotted with black shining" spots, which are 

 due to magnetite that has made an effort to crystallize. Very large and 

 perfect crystals of magnetite are found in chlorite schist at many locali- 

 ties, though not, as I am aware of, in our state. In varieties from Lisbon 

 and Raymond the chlorite is recognizable as a green, foliated mineral. 

 Various sulphurets are liable to occur in chlorite schists. For example : 

 about the Dalton copper mine the schists are filled with sulphurets of 

 copper. 



Remarks concerning the Greenstones. I think it has been already 

 plainly shown that the prevalent rocks in the valley of the Connecticut 

 possess a type that separates them quite sharply from those that occupy 

 the interior of the state. The interior is characterized by rocks which, 

 whether massive or schistose, are highly crystalline ; but the valley re- 

 VOL. IV. 30 



