114 GEOLOGICAL AND MINERALOGICAL NOTES. 



these outcrops the rock is granitic in character and con- 

 tains considerable quartz with hornblende and biotite. 

 The porphyritic feldspar is often quite fresh and glassy 

 and therefore this rock, or the series of outcrops last men- 

 tioned, if studied by themselves in the field, would have 

 every appearance of fine-grained hornblende-granitites. 

 Several outcrops in Beverly and Essex, which are of the same 

 type, are seen to be varieties of the augite-syenite group. 

 Another phase of these rocks, as observed in the field, is in 

 the form of massive flows of the micro-syenite previously 

 mentioned. Certain outcrops of this form are seen at 

 Conomo, Essex, Blind brook, Bray wood, West Gloucester, 

 at the hill south of the Cape Ann forge -works, and ex- 

 tending to the outcrop used for road building by the city 

 of Gloucester. Another extensive outcrop is seen from 

 Rocky Neck, East Gloucester, extending across Pleasant 

 avenue and East Main street to Bass Rocks, near the cor- 

 ner of Fair View avenue and again on Salt island, Briar 

 Neck and Emerson's point, Rockport, and extending to 

 Gap Head in the village of Rockport are seen tongues and 

 veins of this same flow structure. Smaller masses from 

 ten or twelve feet long and half as wide to as many rods 

 in length and width, are seen on all parts of the area cov- 

 ered by these syenites. There are also several intrusive 

 dyke rocks which must bo classed as rocks of more recent 

 age than the mass of this augite-syenite, one of which 

 proves to be a phonolite dyke rock of the type called by 

 Rosenbusch, 1 tinguaite. This dyke cuts the hornblende 

 grauitite 200 yards southwest of Singing beach, Manches- 

 ter. On the surface this rock has weathered to a dull 

 whitish gray with numerous porphyritic feldspar crystals 

 standing out upon it. In the fresh rock the color is a 

 greasy olive green, in texture it is very compact and ex- 



i Min. Phys., Vol. n, p. 627. 



