WARREN. — ALKALI-GRANITES AND PORPHYRIES. 255 



changed into microperthite or a fine mixture of the two feldspars. 

 Both the quartz and feldspar, particularly the former, originally 

 possessed rather sharp outlines and the quartz shows less resorption 

 than in many parts of the porphyry. Flow structures in the ground- 

 mass are very pronounced but there are no indications that the rock 

 was ever, even in part, glassy. 



As already noted, a characteristic of the porphyry near the contact 

 is the presence of what look like inclusions, or of streaks and spots of 

 different color and texture from the matrix. These are in large part 

 unquestionably parts of the porphyry itself and the microscope indi- 

 cates that they are in large part fragments of the immediate contact 

 rock. Sonie of the streaks show evidences of much recrystallization, 

 and seem to be drawn-out and recr\'stallized fragments. At the con- 

 tact with the aporhyolite are found many small rounded or subangular 

 fragments which megascopically seem to be certainly pieces of the 

 aporhyolite; microscopically however, they do not show precisely the 

 same structures, nor are they like the other inclusions of the porphyry 

 itself. They are believed to be parts of the aporhyolite subsequently 

 recrystallized and otherwise changed during its inclusion in the hot 

 porphyry mass. At a number of points, where at present no contact 

 with other rocks is to be found but which from their structure show 

 conclusively that a contact was originally only a short distance away 

 (vertically), the brecciated character of the porphyry is most striking. 

 In such, for example, a short distance from the porphyry -aporhyolite 

 contacts on the small knolls south of Wampatuck Hill and again in 

 the extensive ledges northwest of the aporhyolite contacts on Heming- 

 way Hill, the finest example of the brecciated porphyry are to be 

 observed. In these cases the matrix is a quartz-feldspar porphyry 

 with marked flow structure and of the type found two or three feet 

 distance from the actual contacts. The texture of these inclusions is 

 usually quite irregular, and it is doubtfid if any of them represent 

 original textures. Many of them appear to have been drawn out 

 and moulded, as it were, by the enclosing matrix. In such there has 

 been much recrystallization of the original constituents. Growths of 

 aegirite and the two feldspars are common, normal to the surfaces of 

 the phenocrysts, and to the margins of the inclusion itself. The 

 aegirite and microperthite form curious radiating intergrowths and 

 in some, a poikilitic intergrowth of aegirite and albite resembling the 

 "diabase" structure, may be seen. Many of the inclusions contain 

 what appear to be vein structures and some are, in common with the 

 enclosing porphyry, crossed by minute quartz veins. Fluorite is pres- 



