1892.] NATURAL SCIENCES OP PHILADELPHIA. 177 



At the quarry near 38th Street, one specimen contained six 

 crystals within 3x4 inches, tlie crystals measuring upwards of an 

 inch in length but being rough except upon the tabular surface. 



On the Pennsylvania Railroad, about 3(ith Street, was a small 

 quarry in mica schist. Here was found a rock formed of garnet in 

 mitiute crystals of much brilliancy and of a yellowish-red color 

 under the microscope but of a dark red in mass. It varied from 

 almost pure gai-net to a gneiss containing minute garnets. 



In granitic veins or beds in these schists the mica is generally 

 muscovite, intermixed with a very dark, nearly black mica, and the 

 two occur intercrystallized, occasionally in remarkable specimens 

 some of which are figured in the Keport of the 2nd Geological Survey 

 of Pennsylvania, Vol. C\ In much of the muscovite, hexagonal 

 rhombs, invisible or rarely visible to the naked eye, appear under 

 the microscope. On the northwesterly border of these schists 

 bucholzite, forming a schist, is abundant, especially near Park 

 Station, Schuylkill Valley Railroad. In a quarry south of the 

 Station, and west of the railroad, chalcopyrite, malachite and chry- 

 socolla occurred in hornblende gneiss interstratified in the bucholzite 

 bearing mica schists. 



Between these schists and the overlying gravel is frequently 

 found a black friable conglomerate, the cement of which is wad 

 containing cobalt. It can be found in many places. 



Included in the mica schists are strata of hornblende gneiss, 

 sometimes nearly pure hornblende. Immediately above the old 

 Columbia Bridge in hornblende gneiss was the well-known laumon- 

 tite locality. Good specimens were obtained on only two occasions, 

 the first when an ice-house was built there about 1850 and the rock 

 was quarried to make room for it and to build it, and many years 

 subsequently, when the first ice house having burned down, a larger 

 one was erected in its place. Mehlzeolite was abundant and may 

 still be obtained, but well crystallized laumontite was rare. 

 Good crystals, however, were obtained measuring over three-quar- 

 ters of an inch in length, together with indifferent specimens of nat- 

 rolite and heulandite and of crystallized quartz. 



As an efflorescence on these hornblende rocks alunogen and halo- 

 trichite occur occasionally, but on the Pennsylvania Railroad at 

 59th street there was an old quarry in a peculiar pyritiferous gneiss 

 andfelsite. This quarry was opened for railroad ballast, for which 

 purpose the rock was used to a considerable extent before its rapid 



