606 AUTHENTIC HISTORY 



of nearly pure silicious sand. It rises in a bold ridge ending in a precipitous cliif at 

 Chicques on the Susquehanna, a mile and a half above Columbia. This formation ex- 

 tends eastwai'd from the river towards Rohrerstown and between Silver Spring and 

 Mountville. It also appears between Lancaster and Neffsville, and in tlie eastern por- 

 tion of the county, on Laurel Hill, extending into Berks County. The Hill in the 

 extreme northeastern corner of the county is also an upheaval of this peculiar formation 

 and corresponds with the South Mountain in Berks County, being the lowest in the 

 Palteozoic period. From the Chestnut Hill Ore Banks many thousand tons of Iron Ore 

 (argillaceous oxide and hematite) have been taken from the overlying clay. Xumerous 

 other localities exist throughout the county, where Iron Ore is found, commonly along 

 the borders of the Limestone formation. The curious calcareous rock, called Potomac 

 Marble, (Breccia) occurs north of Manheim and east of Bainbridge. Argillite (or 

 clay slate or roofing slate) is found at Peach Bottom, on both sides of the river and 

 inferior qualities occur in Rapho and Peun Townships, but the laminated structure is 

 found defective to a great degree. 



Considering the extent of the Limestone Valley, between the gneiss and red sand 

 stones, and that in the opinion of geologists most limestone was formed from the cal- 

 careous relics of living species accumulated in oceanic waters, like the coral limestone 

 of the present period, and partially protected by barriers from the incursion of detritus, 

 it is probable, therefore, that this valley was once an arm or bay of the Atlantic Ocean, 

 and now constituting the most valuable and fertile portion of the county for agricultural 

 purposes. The lower or southern portion of the county, like that on the north, is much 

 improved by liming. Belts of limestone are found near New Providence and at Quarry- 

 viUe. Gneiss has much the composition of Granite, but with the Mica more or less 

 distinctly in layers. As the Mica is in scales, a gneiss rock breaks most easily in the 

 direction of the Mica layers, tlms affording slabs. As the earthy matter of all soils has 

 been produced by the gradual decay, degradation, or crumbling down, of previously ex- 

 isting rocks, it follows that whenever a soil rests immediately upon the rock from which 

 it has been derived, it may be expected to partake more or less of the composition and 

 character of the rock. I shall not attempt to speculate on the cause and description of 

 the diversified rocks, the convulsions to which they were subjected, in a remote period 

 of the woi'ld's history, the faults, upheavings, &c., these subjects being accessible in the 

 various books and treatises on geology. 



MINERALS or LANCASTER COUNTY.i 



Arranged according to the last edition of Dana's Mineralogy. To give the general 

 reader an idea of the nature and composition of each mineral, its constituent elements 

 are stated in a parenthesis, without regard to chemical combination. When the 

 occurrence of a mineral is rare, or the locality new or doubtful, the authorities are given 

 in initial letters : D. standing for Dana; K. for Kevinski; R, for Miles Rock; Bcb. for 

 Reepper and W. for Captain Williams. 



L NATIVE ELEMENTS. 

 1. Gkaphite, or plumbago, ("carbon,) K. 



IL SULPHIDES. 

 Galenite, or galena, (lead, sulphur. ) 



1. Contributed by Mr. J. B. Kevinski. 



