186 On the Mineralogy of New York Island. 



localities, so much increased by nearly related or questionably 

 distinct minerals, most of them being well characterized. Nor 

 are the varieties less interesting in hind than in number. The 

 larger portion of them are, it is true, of the common species, 

 but some of them are rare. 



With two or three exceptions, all the minerals of which I 

 shall make mention in this paper, occur on our island in place, 

 though it may not be proper to name it as a locality in the 

 sense in which the term is commonly used, not so much, how- 

 ever, that they do not exist, as because of the fact that a local- 

 ity which promises an abundant supply at one time, may be 

 shortly afterwards covered with buildings, thus obliterating all 

 traces of the mineral having ever been found. 



The area to which my own explorations have extended, is all 

 embraced between 37th and 59th streets, except a passing 

 glance at the fragments of rock scattered along the track of the 

 Hudson River Railroad. 



It is more than probable that the next ten years will see 

 these localities swept away before the advancing tide of ware- 

 houses and dwellings, and a search for minerals on this part of 

 the island will prove as fruitless as it would now be at Cor- 

 lears Hook, a locality famous in Mr. Cozzens's time. 



No attempt at order or arrangement will be here made, other 

 than to mention first in order the species most commonly occur- 

 ring, and closing with those of which but a few specimens have 

 been found, and those reported to have been found heretofore. 



Mica occurs, not only as a constituent of our granites and 

 gneiss rocks, but it has been found in plates eight or nine inches 

 in diameter, at the quarry near 2d avenue, between 42d and 

 43d streets, and in the Central Park near the old reservoir. 



Some of these plates show very distinct hexagonal markings 

 internally, caused by impurities symmetrically arranged parallel 

 to the sides of crystals of Muscovite. Other smaller plates 

 have their surfaces inlaid with white radiating or interlaced 

 acicular crystals or fibres which are probably feldspar, or 



