1880.] NATURAL SCIENCES OF PHILADELPHIA. 313 



ON PHILADELPHITE (Sp. Nov.). 

 BY HENRY CARYILL LEAYIS. 



The mineral to which the above title has been applied was found 

 by the writer four years ago, in what was then a quarry of horn- 

 blendic gneiss, close to the boundary of the Twentj^-second Ward, 

 Philadelphia. The locality is on Germantown Avenue, at the 

 bridge crossing of the Germantown and Norristown Railroad, 

 near Waj-ne Station. The quarry is now walled u^d, and is used 

 as a coal and lime yard. 



Geologically, the locality is just at the base of the terrace of 

 metamorphic rocivs which bounds the drift formations underlying 

 the greater part of the city. Quaternarj^ clays, boulders of the 

 Champlain period, and tertiary gravels appear within a hundred 

 feet of the quarry, and the waters of those different epochs have 

 successively eroded the hill rising above it. This hill, here called 

 Neglejf's or Logan's Hill, about 225 feet in height, is part of the 

 same hill or " Upland Terrace,'' which, trending nearl}' northeast 

 and southwest, has been traced continuously from here into Mary- 

 land, on the one side, and across New Jersey on the other, and 

 Avhich, though composed of quite different rocks in different places, 

 forms throughout, the boundary of the post-jurassic formations.' 



The rock at this place is a hard black hornblendic gneiss, subject 

 to decomposition in its upper portions. It is well exposed in the 

 cut on "Waj-ne Street, where numerous minerals occur, and it is 

 the same which is quarried at Frankford and at MoKinney's 

 quarry, both noted mineral localities. In its altered state it 

 crumbles easil}-, and when heated exfoliates. In this condition, 

 after being crushed in a mill between heavj^ iron rollers, it is 

 sometimes used as a building sand. 



The mineral here described as PhiladeJphife belongs to the ver- 

 miculite group of hj'drous silicates. It occurs both disseminated 

 in scales throughout the gangue-rock, and also in seams, an inch or 

 more in thickness and many feet long. Associated with it in the 

 same quarry are crystals of sphene, epidote and hornblende, and 

 specks of chalcopyrite. It has been found in small quantities also 

 at Waj'ue Street, at McKinney's quarry, and in Germantown. 



^V. Proc. Miu. and Geolog. Section Acad. Nat. Sci., Phila., Nov., 1878. 

 21 



