1892.] NATURAL SCIENCES OF PHILADELPHIA. 183 



brilliant ; rarely it is l)eautifnlly opalescent, resemblino^ labra- 

 dorite, or even more closely resembling tbe microcline of Norway ; 

 muscovite, rare, of a bright emerald-green color ; phlogopite 

 abundant, but not in good specimens ; woUastonite, massive, at one 

 time abundant, but usually rare ; garnet, massive, not common ; 

 pyroxene in its varieties, salite, fassaite ; coccolite abundant ; sphene 

 in crystals up to an inch in diameter, some quite good, poor speci- 

 mens abundant; scapolite chiefly in its variety ekebergite, but also 

 in rough crystals, the former abundant; moroxite ; zircon very 

 rare, but in beautiful crystals ; molybdenite has been reported from 

 this quarry but I think graphite has been mistaken for it ; gypsum 

 in poor specimens formed by the action of decomposing pyrite on 

 the limestone. 



The graphite, phlogopite, pyroxene, etc., occurred in the lime- 

 stone often in bands an inch or so wide and a few inches long and 

 remarkably contoi'ted ; so much so, that sections roughly broken 

 would occasionally closely simulate letters of the alphabet and the 

 late Mr. Vanartsdalen used to exhibit with much pride the name 

 " George Washington " in these natural stone letters remarkably 

 ])erfect except in such details as the cross of the A. 



In the Laurentian at Trenton and also at Camp Hill near Willow 

 Grove small zircons occur, also, in many places loose in the soil. 

 I know of no minerals in this belt elsewhere excej^t the ordinary 

 constituents of the gneiss: quartz, generally bluish or milky, ortho- 

 clase, a triclinic feldspar, hornblende, magnetite and garnet, and 

 also, at one locality near Radnor Station in a trap, labradorite and 

 hypersthene. 



Northwestward of the Laurentian for nearly its whole extent is a 

 limestone valley in which, or bordering it, are schists, those near the 

 Laurentian very closely resembling the Manayunk and Chestnut 

 Hill schists, and in many places near the limestone, unctuous clays 

 carrying much limonite. In the limestone many quarries have been 

 opened, some of them large and deep, especially along a line near 

 the southeastern margin, where a bed of the limestone has been con- 

 verted into marble. The explorations for iron ore have been more 

 numerous than extensive, but in some places vast quantities have 

 been taken out and used chiefly at adjacent furnaces. 



At the limestone and marble quarries there is almost nothing of 

 mineralogical interest : calcite in poor crystals, small quartz crystals, 

 damourite in sheets and coatings comprise all, with the following 

 exceptions : — 



