PETROGRAPHICAL PROVINCE OF ESSEX COUNTY 1 15 



phic, the development being thick tabular, and a radiated arrange- 

 ment quite common. The dark blue hornblende is present here 

 in larger grains, but less abundant, while the green pleochroic 

 aegirite, showing the usual characters is fully as abundant as it, 

 and in places more so. The aegirite does not occur in needles, 

 but mostly in stout, irregular anhedra, and only occasionally in 

 rough prisms. Small crystals of a yellow-brown, highly pleo- 

 chroic biotite are also seen. There are also numerous small, 

 slender needles of a bright yellow pleochroic mineral, often 

 arranged in stellate groups. Their pleochroism varies with the 

 depth of their color, the deepest showing a reddish-yellow par- 

 allel to the length, and a lighter greenish-yellow perpendicular 

 to this, while the paler ones show scarcely any pleochroism. 

 These are the same which were thought to be either apatite or 

 rosenbuschite in the former description, but here their larger 

 size and more intense coloration permits of a better examina- 

 tion, and it seems that they are to be referred to astrophyllite. 



A solvsbergite of a somewhat different type is that forming 

 Shaler's Dike 182, near Pigeon Cove, on Cape Ann. The dike 

 itself is three to four feet wide, with strike N. 73 W. At 

 one place a tongue of granite about ten feet in length protrudes 

 into the dike. In this tongue, as well as immediately outside 

 for a distance of twenty feet along the dike and a foot from it, 

 the granite has been squeezed, and a gneissoid structure devel- 

 oped, the foliations on the outside bending around towards the 

 tongue and being parallel to its length within it. Examined in 

 thin section, the quartz and feldspars of this gneissoid granite 

 are seen to have been squeezed, crushed, cracked, and frequently 

 drawn out into lenticular shapes, exactly as in many gneisses. 

 It is remarkable that such a squeezing should have taken place 

 over such an extremely limited area, the granite outside of the 

 gneissoid portion and on the other side of the dike being abso- 

 lutely normal in character. 



But to return to the dike. This is dark gray and compact, 

 with a few small phenocrysts of aegirite and feldspar. In thin 

 section, it is seen to be composed of a pale greenish hornblende, 



