238 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



The ilbrolite-schists are deep-brown biotite-schists, in wliicli the red- 

 brown shade of the blotite is very characteristic. A fine, silky fibrohte is 

 very abundant. Deep-red garnets are common, and it is largely due to their 

 ready decomposition that the schists have always at surface a very nisty 

 appearance. Nodular masses of a perfectly fresh and limpid moonstone, 

 often 20-30"" across, and generally consisting each of a single untwinned 

 crystal, appear at times abundantly in the schists, whose layers wrap round 

 the nodules so that they seem like pebbles. They are often surrounded by a 

 border of sugary, white, granular feldspar, plainly formed by the crushing of 

 the large central mass and the slight displacement of the fragments produced. 

 This displacement becomes at times considerable in the direction of the 

 bedding; and the granular material is drawn out in tails forming complete 

 "auo-en," wliich, with their centers of orthoclase as limpid as calcite, stand 

 out in marked contrast with the deep red-brown of the schist. They inclose 

 occasionally garnet and graphite, but I do not recall an inclusion of fibrolite. 

 Graphite in minute scales is everywhere present in the rock and is at times 

 quite abundant. 



PETROGEAPHICAL DESCRIPTION. 



Mlca-scMst from Ware. In the bluff near the contact of mica-schist on 

 hornblende-schist, 175 rods southwest of B. Bond's house, is seen a black, 

 fine-grained schist with wavy, shining lamination surface, which may almost 

 be called an argillite, with rarely deep-red garnets and large porphyritic 

 spots of white feldspar. 



In section the dark color is seen to be due partly to trains of coaly 

 matter, but more to the dark color of the biotite scales, which are dark 

 olive-green in thin plates. 



The garnets are apolar and without inclusions. The feldspar is ortho- 

 clase, with no trace of microcline. The rock is very interesting from the 

 pseudofluidal structure developed by the gradual growth of the orthoclase 

 in the mass. The centers are large, rounded or quadrangular masses of feld- 

 spar, showing at times very faint undulose extinction. At either end are 

 grouped a congeries of intergrown grains variously arranged optically, and 

 tapering away to form with the central pieces "augen," around which 

 trains the mica-scales curve. Outside these other bands of feldspar grains 

 appear, and converge in either direction to meet and inclose the central 

 band of mica scales. Outside this another band of mica scales widens out 



