1892.] NATURAL SCIENCES OF PHILADELPHIA. 185 



used thus^in[most of the larger buildings for mauy years. Minerals 

 are rare in this rock. In seams, poor quartz crystals and pyrite 

 occur, with occasionally small, but very perfect and beautifully 

 modified crystals of calcite. In one seam, near the river, about 

 1866, a few remarkable crystals of calcite were found, being perfect 

 and doubly terminated hexagonal prisms, with trihedral summits. 

 Aragonite occasionally lines crevices, some specimens being of much 

 beauty. 



Wiiite cleavable calcite occurs. Phyllite was found in this lime- 

 stone in 186-4 near Plymouth. In the Chester valley fluorite occurs. 

 At Potts' landing galena is said to have occurred in the limestone. 



At the limonite mines adjacent to this limestone belt few minerals 

 occur other than the limonite and that usually in specimens not 

 worthy of a place in a mineralogical cabinet. An exception to this 

 was a mine opened near the Edge Hill furnace on the North Penn- 

 sylvania Kailroad in which at one time a deposit of geodes of limo- 

 nite of exceptional quality was met with. At this time, besides the 

 limonite, which was in beautiful specimens, the geodes were found 

 lined with fine specimens of gothite, turgite and velvet manganese, 

 psilomelane and braunite. 



In 1855 at Colwell's iron furnace on the northeast bank of the 

 Schuylkill at Conshohocken, a few very fine specimens of cacoxeniie 

 were found. This came undoubtedly from the immediate vicinity, 

 but from what particular spot could not be ascertained, as ore was 

 hauled to the furnace from many openings. 



In a thin stratum on both sides of the Laurentian and near it, 

 hornstone or chert occurs, at times in large quantity, particularly 

 northwest of Chestnut Hill, on the Roberts Road southAvest of the 

 Old Lancaster Road near Bryn Mawr, and on the Mattson's Ford 

 Road west of Montgomery Avenue, on the line between Upper and 

 Lower Merion, Montgomery County. 



In the township of Upper Merion, close to King of Prussia, quartz 

 crystals were exposed in a cut of the Trenton Cut-off Railroad, west 

 of the road to Radnor. About two miles further east on the same 

 road, and again about a mile from the Schuylkill a quartzose rock 

 filled with cavities studded with quartz crystals was met with in 

 great quantity. In a similar, if not the same, rock near Henderson 

 Station, Chester Valley Railroad, occurred the fossils for which that 

 locality is noted. 

 13 



