1898.] 



NATURAL SCIENCES OF PHILADELPHIA. 



485 



THE OCCURRENCE OF MARCASITE IN THE RARITAN FORMATION. 



BY S. HARBERT HAMILTON. 



The Gault formation of Folkstone near Dover, England, has long 

 been known to produce the form of marcasite known as " spear head 

 ore " from its apparent close resemblance to this weapon. So far as 

 I can ascertain this form of marcasite has never been observed in 

 this country where it occurs under similar circumstances as in 

 England. 



The beds of the Raritan formation at Sayreville, near New Bruns- 

 wick in New Jersey, which are largely worked for clay and kaolin, 

 contain a considerable amount of pyrite usually in the form of balls, 

 and concretions, in many instances resembling coprolites. Imbeded 

 in the plastic clays associated with these pyrite nodules were found 

 perfect specimens of the spear head variety of marcasite, very closely 

 resembling in size and appearance those from the foreign locality 

 already cited. In some specimens the marcasite twins are implanted 



upon pyrite; again, crystals of marcasite were 

 studded with minute cubes of pyrite illustrat- 

 ing the pseudo-morphism between these 

 dimorphous ferric sulfides. 



The specimens here described were ob- 

 tained upon a joint excursion of the New 

 York and Philadelphia mineralogists to this 

 locality under the guidance of Mr. John A. 

 Manley of New Brunswick, who collected the first specimens. 



Fig. 1.x 2. 



