MARYLAND GEOLOGICAL SURVEY 



97 



a half mile west of Sylmar, north of the State line, two feldspar 

 quarries, the Tweed quarry and the Walker quarry, are being worked 

 in a vein striking east 60° south. North of Sylmar are some aban- 

 doned openings. At the fork in the road, three-eighths of a mile east 

 of Kock Springs, are two feldspar openings in a vein some six to eight 

 feet wide, which have been abandoned for three years. They are 

 known as the Tweed quarry and the Riley quarry. The serpentine 

 bordering the vein has altered to talc. In the spring of 1901 a pro- 

 ductive opening was made close to the abandoned Tweed quarry. 

 The vein strikes 1ST 30° E. The spar is hauled to Conowingo and 

 thence shipped to Trenton. 



About one and a half miles east from Rock Springs, on the edge 

 of the serpentine, is the Taylor feldspar and flint quarry. This vein 

 strikes northeast-southwest and has considerable width. The material 

 is shipped to Trenton, New Jersey, and to Liverpool, Ohio. The 

 quarries are idle at present. 



Magnesia has also been mined in the serpentine, but only in small 

 quantities. The openings, which are now abandoned, are situated 

 in the Pennsylvania extension of the serpentines. The iron ores, 

 limonite and hematite, have been mined in the serpentine of Penn- 

 sylvania,, but the Cecil county serpentine shows no iron ore pits. 



On the roads from Conowingo to Rock Springs and from Cono- 

 wingo to Pilot, there are pits in the serpentine made in search of 

 gold ore, at the instigation of a syndicate known as " The Klondike 

 Company." This company purchased the option on considerable 

 property to the north of Conowingo with the expectation of finding 

 the rocks richly auriferous. The results did not meet their expecta- 

 tions and the company has been inactive for more than a year. 



BIKE ROCKS AND OTHER INTRUSIVES IN THE GRANITE-GNEISS. 



From the mouth of Rock Run to Perryville the granite-gneiss is 

 thoroughly penetrated by dikes varying from one foot in width to 

 several hundred feet. There are two just above Rock Run four feet 

 in width striking N 45° and !N" 50° E, respectively. One-eighth of a 

 mile south of Rock Run there occurs a dike eight and one-half feet 



