100 THE CRYSTALLINE ROCKS OF CECIL COUNTY 



The fresh material is light grey, hard, compact, aphanitic, with 

 inconspicuous quartz and feldspar phenoerysts. An analysis and a 

 petrographic description of this interesting intrusive are given on 

 pages 136-139. 



A meta-gabbro dike of considerable width can be traced inter- 

 mittently across the county from Zion to Newark, Delaware, where 

 it shows itself to be an offshoot from the Delaware gabbro mass. 



An offshoot from the Cecil county gabbro occurs two miles west 

 of Eising Sun on the road to Porter Bridge. 



These are the more important of the many meta-gabbro dikes in 

 the granite-gneiss. 



INTRUSIVES IN THE GABBRO BELT. 



The intrusives in the gabbro belt are of a more basic character than 

 those in the granite-gneiss. One-fourth of a mile south of Conowingo 

 Station there is a dike of light green meta-pyroxenite, about forty feet 

 in width. This is followed to the south by a less altered pyroxenite, 

 about twenty feet in width, and this in turn is succeeded by a dike 

 which has altered to steatite, or soapstone, not more than twenty-six 

 feet wide. A squeezed micaceous vein intervenes between this steatite 

 and a similar eighteen-foot steatite dike on the south. This is followed 

 by a pegmatite vein, eighty-four feet wide, and some more soapstone 

 rock, forty-four feet in width. This soapstone dike is opposite the 

 watchman's box, and after an interval of approximately forty feet of 

 norite, a third dike of soapstone occurs some thirty feet in width. 



About a quarter of a mile to the south, at the second rock-cut 

 below Conowingo and shortly before the quartz-hornblende-gabbro 

 belt is reached, there is a pyroxenite dike approximately sixty feet 

 wide. A pyroxenite dike, which outcrops just east of Oakwood, is 

 probably its continuation, while two small steatite dikes outcropping 

 southwest and west of Oakwood appear to be the continuations of 

 two of the steatite dikes observed below Conowingo. 



DIABASE DIKES. 



Beside these altered dikes there is a fresh diabase dike which 

 extends interruptedly in a northeast-southwest course across the 



