SERPENTINE AT E ASTON 



423 



An analysis of the rock as a whole f^ave the following 



SiO, = 53 



58 







AW, = 13 



56 







Fe,0;, = I 



48 







FeO = 4 



75 







CaO = 8 



20 







MgO = 8 



93 







K,0 = 2 



37 







Na,,0 = 3 



.08 







P.O, = 



17 







Mn^O^ = . 



92 







H,0 = I. 



33 



Sp. gr., 



2.89/ 



98 



37 



On comparing this with analyses of other~syenites, it is found 

 to contain about the average amount of Si02, to be low in 

 AI2O3, but unusually high in magnesia and lime, having of the 

 two together over lyfo, while most syenites contain only from 

 2fo to 6fo. In this respect it resembles Weed and Pirsson's 

 shonkonite of the Highwood Mountains, Montana. In general, 

 however, it quite closely resembles some of the finer grained 

 augite syenites of Norway, described by Professor Brogger as 

 occurring in connection with the nepheline syenites of the Chris- 

 tiania region, for which reason perhaps it would seem natural to 

 associate it genetically with the well-known nepheline syenite 

 of Beemerville, N. J. A careful search for other occurrences 

 of the rock in the region about has failed to discover it. 



The serpentines and talcs of Chestnut Hill are all of them 

 associated with a system of faults which follows the trend of the 

 ridge. Within a distance of two miles north and two miles 

 south of Easton there are four distinct thrust faults, all of them 

 of types described by Mr. Bailey WiUis in his ** Mechanics 

 of Appalachian Structure" as occurring in "The District of 

 Folding and Faulting of Virginia, Tennessee and Georgia." ^ 



1 This analysis was made by Mr. Richard K. Meade, assistant in chemistry in 

 Lafayette College, Easton, Pa. 



2 Thirteenth Annual Report, Part II, of the Director of the U. S. G. S. for 

 the year '9i-'92. 



